I worked out how to do this terrific Issuu application that Gabi Campanario, Isabel Fiadeiro and other Urban Sketchers have been making virtual books with. I used CorelDraw to place the sketches on different pages, add titles etc, then saved it as a PDF before uploading it to Issuu - Voila! - a book! I found I had to reduce the images to 100 dpi otherwise it takes forever to upload. To turn the pages you click on the little arrow on the right. To see a bigger version click on 'View in fullscreen' in the middle of the window.