A few weeks ago I found a website that blends the two beautifully.
Its called Goodreads. (You may have noticed the book list in the left column) It allows me to list all the books I want and categorize them. So far I am still in the 'add books' phase but soon I will write reviews for our favorites. I can check out friends bookshelves to get ideas on what we should read next and read others' reviews on books I am thinking about getting.
Sound like fun to you too? Go check it out! And let me know if you sign up so I can add you to my friends list.