Changing the numbers is what works for me. Here are the full paths for BPL's sites and you can spot the numbers that need to be changed in order to switch:
http://digitalbooks.brooklynpublicli...-DEA86D0A9816/40/20/en/Default.htm Mobile
http://digitalbooks.brooklynpublicli...-DEA86D0A9816/10/50/en/default.htm Classic