My favorite at this point is Witch reader (https://github.com/jpirnay/witchhunt-reader). All the features of Cross-point, with better book rendering, and more features. I've tried a lot of the various alternatives, and keep coming back.

If you want all your book series displayed together, AALU (https://github.com/dawsonfi/aalu) might be worth a look.

And Crosspoint OS itself is still really nice.