Reddit reviews Magic - The Gathering: Gerrard`s Quest

Dominaria has perhaps the *most* lore associated with it, given that it was the primary plane for most of Magic's history (pre-'mending'). There's a ton of books from those blocks (some are even good). I always thought the Rath and Storm anthology was the best MTG story/book money could buy, back when I was into that sort of thing. The Dark Horse graphic novel Gerrard's Quest covers the same ground and is also acceptable (and a much quicker read).

After that you can probably be forgiven for skipping the Mercadian Masques books (though I will defend the Nemesis book to my dying breath), but the 3 Invasion cycle books leading to the Apocalypse event were exciting as hell.

The Thran and Brothers War stories are worth checking out just to get the proper appreciation for Urza as a character (though the writing contained within the books aren't especially good).

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This'll get you started, I suppose: https://mtg.gamepedia.com/Dominaria_(plane)