Is this regarding the old ones or the new ones?
For the old ones, I'd start with The Thran, then move onto the Artifact Cycle novels. From there, the three Greensleeves novels are pretty good, and all other stand-alone books can really be read any time. Just knowing the base story around Urza and Mishra is highly important.
For new ones, I don't know because I've only read one.
The comics are actually quite decent if you can acquire them.
In terms of enjoyment, don't skip Time Streams, by J. Robert King. The writing is absolutely exquisite. The worst book, in my opinion, is The Prodigal Sorcerer, by Mark Summer. It has a repetitive literary style, and the story itself is vastly unimportant to the MTG world as a whole. Though, it does give some interesting insights on the viashino race.
July 11, 2019 12:13 p.m.
I would recommend reading the books in chronological order, so that the story makes the most sense.
First is the Artifacts cycle, which is comprised of The Brother's War, Planeswalker, Time Streams, and Bloodlines. These novels tell the story of Urza's early life and his efforts to prepare Dominaria for invasion by Phyrexia.
Next is the Ice Age cycle, which is comprised of The Gathering Dark, The Eternal Ice, and The Shattered Alliance. This entire trilogy is set between The Brother's War and Planeswalker, and actually has little overall connection to the story of that cycle, but still is an excellent trilogy that adds more depth to the story and also introduces important characters in the lore.
Next is Rath and Storm, which is not technically part of a cycle, but still is very important to the overall story, as it is an introduction to the Weatherlight and its crew.
After that is the Masquerade cycle, comprised of Mercadian Masques, Nemesis, and Prophecy, which add further detail to the world and characters.
The Thran set before the Artifacts cycle, but I would recommend reading it just before the Invasion cycle because it would otherwise render the other stories somewhat anticlimactic.
Next is the Invasion cycle, which is comprised of Invasion, Planeshift, and Apocalypse. This cycle details the Phyrexian invasion of Dominaria and is the conclusion to all of the previous storylines.
After that are the Odessey and Onslaught cycles, which are set on Dominaria centuries after the Invasion cycle, but otherwise have little connection to any of the previous stories. They tell the story of the Cabal, Chainer, Braids, Ixidor, Phage, and Akroma.
After that, the following several cycles are all self-contained and have no connection to each other or the previous stories; they are the Mirrodin, Kamigawa, and Ravnica cycles.
After that is the Time Spiral cycle, which returns to Dominaria and details the aftermath of the previous cycles that occurred on that plane.
After that is the Lorwyn/Shadowmoor cycle, which is again self-contained and has no connection to any previous cycles.
Finally, WotC stopped publishing novels for each set and instead published a single novel for an entire block, doing so for the Alara, Zendikar, and Scars of Mirrodin blocks. After that, they did not publish any further novels until War of the Spark, earlier, this year.