I would suggest practicing looking up things in Pub 17. Get familiar with how it is indexed noting that you might think of something by one word but Pub 17 has it indexed by another word that could be used to designate a topic.
Every question on the test is probably covered by Pub 17 or Circular 230 and I understand it is an open book test, but you have to access the information online.
Like a lot of CPE, they probably dwell on a lot of things like "how much is an exemption allowance" which is hardly indicative of your tax-preparation abilities since that sort of thing can be done by your tax program.