The Open Book page image presentation framework is not designed to replace printed books. Rather, it is a free, browsable, nonproprietary, fully and deeply searchable version of the publication which we can inexpensively and quickly produce to make the material available worldwide.
For most effective printing, use the "printable PDF page" link available on each OpenBook page's tool block. The 300 x 150 dpi PDF linked to it is printable on your local printer.
More information on the Open Book is available.