I asked this question about a year ago myself when I first wanted to buy their books, especially since I am from the UK I have to get it from up1, so I pay a bit extra, roughly £19 per book. I bought my first book and was really surprised, the paper quality is really high, far superior then your average manga or light novel book you will find anywhere else, very silky and smooth feeling and thick, and the printing is very fine and sharp so you're always going to see every bit of detail. The jacket of the books are also very high quality and nicely colored. Less than a year on and 30 books owned I can say I have not regretted any of my purchases, the books look very pleasing and are of top standard compared to anything else I own, and I own a lot of books.
Buy your first book if you can afford the 20 dollars, and make your decision, worst case you don't like it and you are 20 bucks short :)
also check out the post FAKKU Books: FAQ, there is some interesting posts on there about how they check their books before printing for color correction and proofing which is interesting, it really shows how much work they put into their books.