It varies greatly on how readable the book is and how immersed I become in it. I read a lot as a kid, but once academic reading became all I had time for, it kind of killed the pleasure of reading for me. Then, once I became a parent, I would fall asleep after a paragraph or two in a magazine.
I only just started reading again last year, The first book I read was non-fiction, but it was about sound and acoustics and noise pollution, so it related to my vocation and I found it very interesting. I read a chapter or two a night.
The next books I read were young adult series that I had enjoyed as a teen, and wanted to re-read from an adults perspective. Those sucked me in and I read through them non-stop at the expense of anything else I was supposed to be doing.
I then read through Colonel Chris Hadfield’s book, An Astronaut’s Guide to Life on Earth at a similar pace to the other non-fiction book I’d read, a chapter or two a day. It’s been several months since I finished that. Hmmm…