If you still have the scans a quick and dirty method would be to use Scan Tailor to straighten them up, align them (either by page number or header) and apply the "up to 99.8%" good enough OCR with ABBYY FineReader 11 -- the accuracy would probably lower with those black and white images, but whatever... At least they compress better than JPGs. The general ball park is somewhere between 10-35 MB, depending on the book - 256 bit cover and all. Definitely an improvement over 300 MB per book...
The quality method would be to proofread the OCR in FineReader, save it as .docx/.odt, do the layout in Word 2010/LibreOffice, track down fonts (which often times is a lot harder than it sounds), vectorize the cover (assuming you know how to use Illustrator/Inkscape) and proofread the final product again in case you may have missed something. This process is a lot more refined and it can output books between 1-3 MB, depending on the book. It can be a little bit time consuming, yes. But it's a pleasure to read such a book.
Last edited by DSpider; 12-17-2011 at 06:25 PM.