Yes, you can do it. It depends on what type of bar code scanner you have. 

If you have a bar code scanner with memory (stores some information directly in the scanner). Then you can scan a bunch of books, connect the scanner to the Mac and then choose Edit-> Add Multiple Books.

If your scanner does not have memory, scan the barcodes into a text file, separate them by a return, then go to Bookpedia-> Edit-> Add Multiple Books... and paste in the whole file. You will notice that the field shows a single entry, but it will take multiple entries and process them.