Looks incredibly serviceable and well engineered. I would expect reasonable and consistent results from the rig. The biggest question would come down to the cameras.
With these kind of rigs (two cameras, not computer controlled, no computer display) your big potential sources of error are either accidentally failing to trigger one camera or cameras losing focus on the page (especially if you are at something like the end of a chapter where there is often empty space in the middle of the page where the camera's auto-focus area is). His solution of using the IR remote should significantly reduce the issue of failing to capture on one camera. Cameras exist with manual focus settings, but they are often pricier or too old to reliably find one worth recommending to others. The CHDK alternative firmware for certain cheap Canon cameras generally adds a manual focus option for the less expensive cameras (though the individual features depend on who is making the firmware build you get).
Another option worth investigating is the newest Raspberry Pi camera modules with external lenses. Those should give you manual focus and the ability to build up an automated workflow you like around things like moving files around and any pre-processing you need. An ~9 mega pixel camera gets you 300dpi resolution on a full sheet of A4 paper, which is a lot more than most books.
Right, step 1 -> get page images, step 2 -> author images into book file. While OCR is obviously useful for search, a rotated phone screen will let you comfortably read a pdf book just fine unless you are talking about something like a textbook, in which case you probably wanted a tablet anyway.
I wrote up a guide on the authoring process using FOSS tools for some Digital Humanities folks a couple years ago: https://github.com/wikey/bookscan
It gives some background on the problem and covers a Scantailor (page crop, rotate, deskew), pdfbeads (compression, book metadata) authoring workflow, with pdftk for some general odds and ends.
With these kind of rigs (two cameras, not computer controlled, no computer display) your big potential sources of error are either accidentally failing to trigger one camera or cameras losing focus on the page (especially if you are at something like the end of a chapter where there is often empty space in the middle of the page where the camera's auto-focus area is). His solution of using the IR remote should significantly reduce the issue of failing to capture on one camera. Cameras exist with manual focus settings, but they are often pricier or too old to reliably find one worth recommending to others. The CHDK alternative firmware for certain cheap Canon cameras generally adds a manual focus option for the less expensive cameras (though the individual features depend on who is making the firmware build you get).
Another option worth investigating is the newest Raspberry Pi camera modules with external lenses. Those should give you manual focus and the ability to build up an automated workflow you like around things like moving files around and any pre-processing you need. An ~9 mega pixel camera gets you 300dpi resolution on a full sheet of A4 paper, which is a lot more than most books.