Reading at work

Hi all. So this is not a request on WHAT I should read, but rather HOW I should read.
I switched jobs about 6 months ago and have found that I have a bit of downtime throughout my work day. I’d love to use that time to read my books instead of just surfing the internet. Problem is I can’t just kick back and open a book in my office. I need to look at least somewhat productive lol.
Is there a website I can view/buy entire books and read them in a .PDF or something similar on my computer?
Sorry if this is a weird request, but I thank you in advance. 🙂

by yeah-not-really