I'm looking to learn as much as I can about the equipment of WWII specifically weaponry. I can find books on the M1 Garand, for example, but not one on all infantry arms even for just one army. I'm probably just bad at research, but I would really appreciate a steer in the right direction.
It all depends on what kind of information you're looking for.
Are you seeking information on production details, factories, numbers, technical processes, differences in various stamps and parts depending on the year/factory, technical details such as how they work, different kinds of ammunition and performance, etc...
... or just a very basic description of each one?
If you're like me, and want very detailed knowledge, getting one or two books (aside from manuals and other sources of information) for each firearm is the only way to go.
North Cape Publications and Collector Grade Publications books are usually great on historical information, though the scope of their books differ slightly depending on the author. Some are slightly lighter on history, if the author is more interested in the technical details, and vice versa, but they're generally quite comprehensive and a very good start. Most of them are focused on original production, with chapters on post-war use, while some have separate books covering that period.
Then there are the self-published books, which is always a risk seeing as anyone can self-publish, but I've struck lucky sometimes. For instance, Scott Duff's book on the M1 Garand is well worth the price and any Ian Skennerton-book I've purchased was worth it. Let it be said, though, that having a publisher is no guarantee of quality, so I'd recommend checking reviews and the reputation of the author/book before buying, regardless of who published it.
If you're more interested in operating the guns, and want more detailed information than what's offered in the original manual, Heritage Gun Books have a few very detailed shop manuals, and I've seen Skennerton as well as others do as well. The Collector Grade books on the MG 34 and MG 42, written by Folke Myrvang, have ample operating instructions for the modern user.
On the other hand, if you're just looking for a basic description of each one, I can't claim to have much knowledge, but I know Ian Hogg wrote quite a few books with various selections, and Osprey Publishing has published a series on WW2 weapons. I'm a bit leery when it comes to Osprey, as they are generally good on the basic facts, but sometimes leave glaring errors in the details.
It all depends on how deep you want to go.