I had personally already moved onto Moon+, even though I like Fabrik better in a few ways.
Moon+'s book syncing isn't as nice.. You have to go browse your network share and download a book to read. If you have a zillion books there, it's probably a better solution. But if you're like me and just put up a new one when you're reading it, Fabrik was nice that it synced it automatically.
But Fabrik was VERY slow opening some books, and some books it would randomly not open.. Moon+ opens them really fast, but it also does some loading between chapters, but it's usually less than a second. Kind of an annoying pause, but better than sometimes waiting a minute or more for Fabrik to open a book at all.
And Moon+ is half off right now, so if you haven't, check it out while it's cheaper. The free version does pretty much anything you need except syncing, so if you want to sync books between devices (and pull them off cloud shares easily) get the Pro.