More of them than not are good in my opinion. Originally I was just posting links to them as they came out after Anons asked for it, but reading Rarity's book made me realize they're actually decent.
Twi's princess coloration book is my favorite, but I can't help but be biased for my favorite technicolor equine. All the books are in here unless I missed something recent:https://www.mediafire.com/file/l43u24xfk736yx3/Books.rar/file
With the show done, comics Corona lagging, and manga volumes having long gaps between I think these are a good thing to go through.