Reddit mentions of Jazz Up Your Japanese with Onomatopoeia: For All Levels

This is the single best book about the topic. Not only does it start with a discussion of sound symbolism in Japanese, but it gives you real definitions for the words, in which case it doesn't just give one or two word definitions but really explains the words and their nuances. In fact for every word it includes whether it is good, bad, or neutral. Most of these Onomatopeia have both sound and mimetic meanings. Such as どんどん being a good example because it's also a low heavy sound. Like the slow beat of a bass drum.

I accidentally spent an hour and a half writing this. Excuse the length, it got a bit out of hand.

First of all take formal lessons. Doesn't matter where or how, learning is considerably easier through assistance and interactions with people. Anyone can learn to read moon runes but a teacher can help with conversation and pronunciation especially which is the most important aspect. I started with weekly out of school classes and for a year I had a family friend tutor who would help me weekly and I can't emphasise how helpful learning through a teacher is.

My total class time was a little unorthodox with 5 years of extra studies in England during secondary school followed by 3 years of Japanese in Australia during high school. The rest has been self studies of kanji and overall reading and listening. I'll go through everything.

Second is to get the Japanese writing system down; hiragana and katakana. Kanji is also important and an absolute must if you plan to read light novels, manga and especially visual novels. My personal preference for a digital kanji dictionary is Japanese which comes with useful features like a touch screen writing kanji search, stroke order for kanji writing, JLPT kanji learning and sorting and most importantly sentence usage examples.

Visual novels are rough because they have sometimes have the unique blend of every day kanji and words before throwing terms like large hadron particle collider and anti gravity particles, (I'm looking at you Aokana.) My personal method for learning kanji has been to get a book and manually create my own list in Anki.

Third is books. Again, the standards you'll find are Japanese for Busy People and the Genki series. I live in Australia, mind, resources may be different in other countries. Other helpful texts down the line include: Read Real Japanese, 日本語擬態語辞典 (A Japanese Onomatopoeia Book, though I'm sure Jazz Up Your Japanese with Onomatopoeia would work just as well) and the last one I'll mention below.

The Japanese Shonen JUMP is an exceptionally useful source if you're able to get a hold of it. Weekly, reasonably prices, recyclable books with pictures to deduce words from context, furigana to help with kanji and a decent art resource if you like drawing. I get a cop of JUMP weekly from Kinokuniya in Sydney if anyone from NSW happens to read this.

Fourth, use the internet! Don't use the net as your primary resource, text books exist and are pricey for a reason. However, there's a ton of great side content online that you can use. One alternative to JUMP is Pocket Shonen Magazine with all sorts of manga in Japanese that provides the lastest chapters for free. It's also home to the rather unique read Nagatoro-san.

You also have options like Japanese podcasts, (I like Anime Cafe Latte), Visual Novels with Japanese subs as well such as Little Busters English Edition and Go Go Nippon!* and Japanese news websites.

Additionally once you get better at reading and writing you can lurk on Japanese forums, YouTube pages and Nico Nico if you want casual chats with fans. When I played through Persona 5, it was nice to talk to other Japanese players in the early days of release and discuss it. It was also helpful that players created a walkthrough website for P5 and various move and frame data for Dissidia which were helpful. Again there are many ways you can learn and utilise Japanese so never underestimate when, where or how you can use the language.

Fifth is Japanese Media. Anime, manga, animation, live action films, books, music, podcasts, anything! Constant and consistent exposure to the language is an incredibly useful method to get down pronunciation and fluency. Anime and manga won't help with casual conversation but will keep the language fresh in your mind and help with pronunciation. An example of difference between representation of pronunciation can be shown in the Chihayafuru live action films, (which are very good!) Kansai certainly has its own quirks that isn't present in your bog standard Tokyo dialect, but the more realistic live action take on kansai, compared to the sporadic and higher pitched anime take is a shocking juxtaposition.

This is getting very long so I'll just through out two YouTuber I haven't put in the text above and a few small useful FAQs I see around.

Abroad in Japan presented by Chris Board is a very fun and insightful series of videos looking into places in Japan off the beaten path. He also has a podcast.

That Japanese Man Yuta interviews various people in Japan about various topics. The interviews are generally subbed and are great for hearing natural speech patterns and word choices.

Q: Do I need to know a lot of Japanese when I go to Japan? A: Not if you're travelling around Tokyo. Anywhere outside train transport and the city is a lot harder to navigate when reading signs. This has been improving over recent years. Tokyo locals can manage a little English but you'll have a far easier time if you know the language.

When I went near Kobe for a Haruhi anime pilgrimage there was a distinct lack of any English whatsoever outside of the train station. Nobody spoke English and all communication was Japanese. You also get to hear some amusing side comments from people in the Japanese if you look foreign enough.

Q: How vital is learning Japanese for games nowadays considering the increasing speed and frequency of translations? A: Recently games I've played or want to play in Japanese such as Persona 5, Gintama Rumble and Girls und Panzer have had English subs in their Asia edition on sites such as Play Asia. Better yet is that some of these games get same date releases. However, sometimes translations can be wonky depending on who was contracted for the translation such as the infamously awful Sword Art Hollow Fragment translation.

Some games like Ao no Kiseki and Zero no Kiseki are only now receiving translations despite being popular games. Did you know there's a PS3 visual novel about using a smartphone to read girls' current emotions? I didn't until my little sister brought it back from Japan for $10 from my favourite store Trader, (it's not that good.) Even larger titles such as Summer Pockets are also left in the wind as to whether or not it'll be translated officially or by fans reasonably soon. There are also an exorbitant amount of games that don't get official or fan translations.

Q: Do I have to become a sub elitist because I know Japanese? A: Nope, contrary to popular belief you can still enjoy dubs but you may find you appreciate the subtext in Japanese that isn't heard in English more often. Playing Square Enix games can be especially frustrating in sub when you realise just how much text can be abridged, (you may actually prefer this in some games however.)

Q: Is there a 2,000 word essay you're avoiding writing? A: Yes and that concludes this post.

Hope this helps, hit me up if there's anything else you want to ask.

Depending on what parts of the language you're interested in specifically, Kodansha makes individual books on adjectives and adverbs, verbs, particles, onomatopoeia, levels of formality, kanji prefixes and suffixes, slang, etc.

Of these, I think the onomatopoeia is the one that far outshines what you might find on the topic in a general textbook.
https://www.amazon.com/gp/aw/d/1568364865/ref=pd_aw_sim_14_of_23?ie=UTF8&psc=1&refRID=4EBPBSHE3WES29Z31JTK

That being said, nowadays most of this information is online, but if you like having it all in one place, or just prefer books as a format it might be useful.

There are thick books about Japanese onomatopoeia. I have this one,
but that one seems to be easier for a start.