Best comfortable book reading chair?

Depends on your taste, and your budget! I love firm chairs, firm sofas, firm beds, etc. When I sit down into a chair or sofa and it feels like I lose my spine, I'll never get comfortable. This is especially true for a reading chair.

Of course, the Eames chair is super expensive, but it's incredibly comfortable (not everyone agrees) and you'll own it forever: https://store.hermanmiller.com/living/lounge-chairs-and-otto...

I also love the Knoll lounge chair. They've got a firm and relaxed option, fabric or leather, ottoman is separate: https://www.knoll.com/product/florence-knoll-relaxed-lounge-...

Also firm, comfortable for long periods, and stylish: https://www.roomandboard.com/catalog/living/chairs/andre-cha...

Here's one that's more plush, something you can sink in to: https://www.roomandboard.com/catalog/living/chairs/hess-leat...

This one is too large and bulky for my taste, but I have friends who own the chair and they love being able to curl up in it: https://www.crateandbarrel.com/lounge-ii-petite-chair-and-a-...

The IKEA Poäng has a pretty good reputation for being a low-cost comfy chair, though you'll want to try one out in person to see how well the lumbar curve works for you.