How to Hold a Book Open
If you find that you have to hold a book, best way to hold a book open is to let it rest on the palm side of your hands held flat. The front cover should be resting on the left hand, the back book cover on the right hand. This approach avoids gripping and evenly distributes the weight of the book across both hands. If the pages of the book are stiff, they may not lay flat with this method.
A better solution is to lay the book on a table or desk in front of you with your hands held flat on the left and right edges of the pages to hold them down. This not only avoids bent, clenched fingers but also avoids the weight of the book on your hands.
Rather than holding a book, you can eliminate pain entirely by listening to the book instead. I didn't often use audio books before I developed arthritis in my hands, but I wouldn't know what to do without them now! Recorded books come in many formats including cassettes, CDs, and files for your iPod, computer or other listening device. And we're not just talking about fiction, there are books of every genre except picturebooks. You can find them online, at your bookstore or at the library. Look for "unabridged" audiobooks so that you don't miss any of the original content.
I find that there are some professional readers I like more than others, but most booksellers allow search by reader / performer. Some audio books that are well done include the Harry Potter series, the No. 1 Ladies' Detective Agency series, and The Lord of the Rings trilogy.
eBooks and eBook Readers
When the Kindle first came out, I thought "How ridiculous. Why would anyone buy a separate gadget when they could just read an ebook on their computer?" I was so wrong. The Kindle was a huge hit, followed by the Barnes & Noble Nook. I recently saw one of these, and I immediately understood the excitement. eBook readers cause less eyestrain which is wonderful, but the real benefit to those who have arthritis is that they are noticably lighter weight than a book. I said "Oh my goodness, even I could hold onto this for a long time. You should tell people with arthritis about this, this is wonderful!" Two separate individuals who were passing by heard me and, at the same time, said, "You're right, that's why I have one -- arthritis." For best results, let it sit on your flat hand rather than gripping it.