Hey there, Sasha!
Source is a gem! Frigates of EVE is likewise fun. It has schematics, design backstory, general information about the navies of New Eden, and a lot of anecdotes, along with a story about a Sisters of EVE exploratory crew. I definitely recommend it. Empires of EVE, meanwhile, covers the player history of the early EVE period. The author did a phenomenal job, so I do recommend it, but it may not be your first move if your main focus is on lore and backstory.
That said, Templar One and the Empyrean Age are not well-loved books. TEA came before T1, so I’d read in that order, but the author, uh, writes with broad strokes, shall we say?
Also, you might check out the Burning Life. It’s a leisurely tour of New Eden, touching on a lot of the major factions. It’s not necessarily the most dashing or engaging story, but it gives you a pretty good feel of the various factions and how they appear to a visitor.
That said, I’d be happy to answer any questions you have! Also, check out Teinyhr’s excellent lore compendium thread. It has a lot of references you might find interesting. :3