Reddit mentions of The Lives of the Great Composers

Ahh, that makes sense, sorry \^\^;

There are books on a huge variety of subjects in music, so it does depend a little bit on what you are interested in specifically. For a broad overview, I liked A History of Western Music - the current edition is the 8th, but much of the materials from the 7th edition are available online. Another book I recommend is Harold C. Schonberg's The Lives of the Great Composers. It is less in-depth, but is written in a more narrative style while still hitting on a lot of the "who's who" in classical music from the Baroque to the 20th century (although it's maybe a tad outdated in the later 20th and 21st century).

Besides those two, I actually don't have any others on the top of my head that are good overviews. /u/m3g0wnz does have a guide to music theory textbooks on the sidebar that details out some of the main texts in that area. And, of course, there are books that specialize on a variety of subjects within music theory and history - Ebenezer Prout's book on fugues is one such example that I've looked at, as well as both the Kennan and Adler on the subject of orchestration. (Actually, Kennan also wrote a book on Counterpoint.)

On the subject of sight-singing, I've used both Rhythm and Pitch and A New Approach to Sight Singing in my aural skills classes - I like the Berkowitz a little better in the way it's organized, but both offer plenty of examples for practice. Alternatively, picking up a hymnal is possibly an easier alternative to sightsinging that gives you lots of tonal material for practice.

With most of my other suggestions, though, you don't really need a book. Print out some scores on IMSLP or pick up a cheap study edition (like this one of Mozart piano sonatas) and work through a harmonic/formal analysis.

With transposition, I think probably just working through some scores on IMSLP would be a good start, as well - I can't think of any other better way to get exercises for that. It's one of those topics that's pretty easy to quiz yourself with as long as you keep yourself honest. :)

Edit to add: As far as specifics of literature, that is obviously pretty instrument-dependent. I am a vocalist, and I usually choose language first and then begin exploring pieces that might work with my current technical goals. I know a lot of instrumentalists treat genre/time period the same way. So depending on your instrument, you may have a different approach, but it helps to narrow things down to a few composers you might like to explore for your instrument, and then seeing if anything works for you. Although be wary - for me I end up getting so involved in lit studies that I have a list a mile long of pieces I want to study in the future. It's a double-edged sword for sure.

Schonberg’s Lives of the Great Composers is a good overview of classical music from the late Renaissance/early Baroque music of Monteverdi and going up to as recent as the 1970s-80s, however it may have been updated since I only have the first edition. Easy to read and does not get technical with music theory too much. Definitely a good read for someone who isn’t necessarily a music student but interested in the subject! The Lives of the Great Composers https://www.amazon.com/dp/0393038572/ref=cm_sw_r_cp_api_i_NOL5Ab9HFARNC

http://www.amazon.com/Lives-Great-Composers-Harold-Schonberg/dp/0393038572

it focuses, obviously, on composers and doesn't talk much about form, harmony, etc. but it's a great read

Harold C. Schonberg - The Lives of the Great Composers

it's called The Lives of the Great Composers, here's a link to the amazon: http://www.amazon.com/Lives-Great-Composers-Harold-Schonberg/dp/0393038572

it's definitely a fun read, I'm only about halfway through it and I feel like it gives a pretty good summary of the lives of the early/really established musicians (bach, haydn, mozart, beethoven, etc.) I'm only just now getting into the sections where it's talking about multiple people per chapter, but he still does a pretty good job of describing them. I think the awesomest part to me is the early parts until it starts going into the mindset of beethoven and how big of a shift it caused. I won't spoil it if you want to read it but it's pretty awesome to see