There are providers [1] that will destructively scan the book for you and return a PDF. If you want to preserve the book, you're stuck using a scanning rig [2]. The Internet Archive will also non-destructively scan as part of Open Library [3], but they only permit one checkout at a time of scanned works, and the latency can be high between sending them a book and it becoming available. FYI, 600 DPI is preferred for archival purposes.
[1] http://1dollarscan.com/ (no affiliation, just a satisfied customer, can't scan certain textbooks due to publisher threats of litigation)