I like the Avatar Legends RPG, and the lore included is great. But I hate how spread out the rules are and how much hunting around I find myself doing. They probably could have put all the rules in a concise, 20-30 pages or less. Then the other hundred or so after that could have the lore.

It's PbtA. Very easy to GM and to play. But it's still hard to convince people to try it, even people who like ATLA, because the rule book looks so long.

I think it depends on the game. I am studying the Blades in the Dark rulebook and really loving the detail. I think what makes a big difference is that the details provided feel like they would actually help with GM prep. This is a first for me. So many modules and rule books provide details while somehow being utterly useless. My advice would be to play test the system and only write down the kinds of details that actually made a difference in your prep and games. There is such a night and day difference I am feeling with this rulebook and I dont think its at all obvious to the casual observer. Got to get out of that author mindset and into a gm one. Thow out all that inspiration drivel and make actual facts out of the world that would matter and lead to plothooks for a campaign. ... that is if you want to, generic systems are good too.

What i really want in books is enough lore and setting to easily make plots. In the book for Myriad song they included 20 planets with quick plot hooks for each. Add to that a good sized monster section with rules to make your own.

Another good book Ninja crusade. They have a few pages of history and one place that includes a list of possible alternate version of important events. Thats really useful as a gm.

Both give me setting and rules to make one shots or campaigns