Reddit mentions of The Illustrated World Encyclopedia of Guns: Pistols, Rifles, Revolvers, Machine And Submachine Guns Through History In 1100 Clear Photographs

It seems like an archaic way to learn about them now, but when I was a kid, I used to buy books like this and just study them for hours at a time.

https://www.amazon.com/Illustrated-World-Encyclopedia-Guns-Photographs/dp/0754831760/ref=pd_sbs_14_2?_encoding=UTF8&psc=1&refRID=JW0ZHJJRAN917V58HJQ6

Battlefield 1 is fantastic. Here's my personal favorite two - books about guns. No, I'm not a gun nut, I just really like military history. The first one goes more into history, while the second has specifications and technical information. Both are really interesting and make a great conversation starter. The best part is as you can see, they're not expensive at all.

As for history, any of - the Smithsonian's - visual history books are fantastic.

A personal favorite of mine, though, is Timeline. It's a gorgeous art book with a timeline of human history. It really helps kind of put things in perspective, and while it's not photographs, the art is really well done and appealing.

As for mycology, check the website of major arboretums near you. I'm lucky enough to live near the Virginia State Arboretum, and they usually have contact emails and are more than glad to recommend books, activities, and even offer volunteer positions to help you turn your interest into a hobby. I'm not sure myself about fungi books, but your local arboretum (usually on a major university campus) or the Virginia Arboretum should be able to point you in the right direction.

For anything else, you can usually find good art books by googling (Subject) Visual History or Visual Compendium, Visual Compilation, Etc. Visual is usually the key word. Even (Subject) Visual Book usually nets some great results.