I can also recommend the Fujitsu ScanSnap product. I used an S500 unit to scan multiple instruction manuals, each maybe 1 to 2cm thick, double sided. I trimmed off the glued binding, then fed the pages through in chunks. Sometimes I would slip in the next stack as it was pulling the last page of the prior stack. Even if it paused after exhausting the currect feeding, it would carry on when I added more pages, with all the pages going into a single output PDF (configurable).

Very few OCR errors, excellent rendering of the diagrams and charts, direct to searchable PDF output. One pass does both sides, colour, grey scale, or B&W. I opted for higher DPI scan quality rather than most compact output file, and I suspect that also helped the OCR accuracy.

Fairly quick overall.

I have yet to unpack my newer Fujitsu S1500 model, but I expect it to be as good or better, both software and hardware.