So I am studying from 4th edition right now, got through up to 13 so far. It is definitely pretty detailed. I also had a skim over the chapter content of 3rd edition using a pdf file, and compared it side by side. Changes in most chapters are minimal to none, the only MAJOR change I see is the plant chapter. The plant chapter in 4th edition is about as half as long as that of 3rd. The 3rd edition goes in more depth for plants. So my advise would be to study the 4th edition, since it does go more in depth than the 3rd edition overall, and supplement the plant chapter using the 3rd edition, or Feralis or KBB. Probably don't focus much on the laboratory chapter of the cliffnotes as well because the DAT doesn't really go into those. To speed up going through this dense book, just do the multiple choice review questions, and don't do the free responses. Do them if you finish the book and have time leftover for further review. Otherwise I would just go straight into destroyer from there.