I'll go on record as saying that the book is legitimate.
The cards don't look too thin to me.
The seller recently sold an interesting signed Bender item:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=180642521529
The bad feedback appears to be mostly communication/shipping problems.
The seller is also selling a signed Cy Young ball, that has been GAI authenticated:
http://cgi.ebay.com/SINGLE-SIGNED-RA...item2a1054a517
If you look in the picture of the Young ball, you'll see an auction description about how this came from the collection of some dude who put it together in the 1920s or 1930s. The scrapbook was probably put together around that time -- obviously a lot of wear and tear to those cards before they were put into the scrapbook.
Neat old book. Would love to have it. But wouldn't pay more than $1,000 for it....