For OCR work you have a number of options depending on how easy it is to remove the pages. If you can't remove the pages then you need to find some way to keep the book flat when you take a picture of each page.
1/ I am assuming that you do not need colour critical photography - this will be for optical character recognition, not accurate reproduction of colour.
2/ Lots of pages, so speed is key
3/ given (1) and (2) above you need some form of copy stand, this link
shows an example of a copy stand - a post on which to mount the camera and lighting to provide even illumination. You can shop around for cheaper versions, however, typically you pay for what you get.
4/ You can use a regular point and shoot camera - the two conditions that you need to bear in mind are (i) you need to mount the camera high enough that there are no distortions (barrel or pincushion) in the image (i.e. don't be so close to the book that you use the most wide angle setting, or so far that it becomes difficult to work) - you probably need to be around 3x the longest dimension of the book - so for an A4 document about 1m should be Ok - but you may need to experiment. (ii) choice of camera...if you need 300pixels per inch, multiply the longest side of the document by 300 and that will tell you how many pixels the camera needs. So for 12" document you need 3,600 pixels on the longest edge of the camera's sensor. I would suggest for A4 any camera at 10Mpix or 12 Mpix would be more than ample.
5/ If you can remove the pages from the book then I would recommend a document scanner which can produce PDF documents from the scans. This could scan a 100 page document in a couple of minutes. You may consider going to a reprographics shop and asking if they can do it for you. We typically use a Canon CLC5151
- though this may be a little outside most peoples price range. Cheaper options exist.