So far the biggest incompatibilities I can see are:
- Picard still mourning Data as dead in 2399 vs Data 2.0 coming to life in 2384
- Seven still having her Borg implants and being actively hostile to Starfleet, implying she didn't return to the Delta Quadrant and there was no Project Full Circle
- The continued existence of the Borg cube and of Borg drones cut off from the Collective, implying the continued existence of the Collective itself
- The implication that Picard and Beverly did not marry and have a child in 2380
- The Romulan Star Empire needing to ask the Federation for assistance evacuating its capital planets seems weird if they're part of the Typhon Pact
- The major events of 2385-2386 are different. Sept.-Oct. 2385 in the Litverse sees the assassination of Nanietta Bacco and the rise and fall of Ishan Anjar, followed in 2386 with the exposure of Section 31 and the purging of Control from Uraei's system. The canonical 2385 now has a major, Federation-changing event occurring in April 2385 in the form of the Synth attack on Mars.
But so far -- and again, we're only two episodes into this, so this could all totally change -- I find myself suspecting that TrekLit authors might be able to reconcile their continuity with the canon. Picard, for instance, may not regard Data 2.0 as an actual continuation of Data, but as a separate being given Data's memories. (Coincidentally, this is how
I view Data 2.0.) If there's nothing PIC episodes actively denying that Starfleet ever returned to the Delta Quadrant, then we can probably keep that in our headcanons. The Caeliar may not have been 100% in their removal of disconnected Borg drones and tech -- if the Collective itself never appears, we may not have any real problem reconciling the Artifact with
Destiny. So far, there's no explicit denial that Picard and Beverly had Rene -- maybe their marriage failed around the time Picard left Starfleet, and she took Rene to raise herself, one of the regrets haunting Picard in 2399? If the Romulans under Praetor Gell Kamemor got too cozy with the Feds, I could see the Pact -- maybe under the influence of hostile Pact members like the Breen or the Tzenkethi -- refusing to help.
We'd probably either have to fudge the dates on 2385-2386 and assume that the events of
The Fall happened a year earlier (which wouldn't bother me --
The Fall's reference to Bacco's re-election in 2384 didn't line up with the established four-year election cycle for Federation Presidents), or we'd have to assume that the Mars attack and the anti-Synth backlash was happening "off-screen" between books, and that the assassination of Bacco maybe contributed to the Federation's reactionary drift over the next decade and a half. Maybe President zh'Tarash lost re-election and the next President was a reactionary in the vein of Baras Rodiyra?
Obviously we'd have to squint and accept a few retcons, but I do feel like it might be possible to reconcile these things so far. (I also feel like the next few episodes are likely to make me eat my words, but it's a fun mental exercise for the moment...)