I'm not an expert but as far as I am aware the syllabus changes on a not infrequent basis. At the very least when the exams went from JAA to EASA a number of topics were shuffled between exams so you will at least need to know what items to learn for which subject.
If you really don't want to buy anything then you could try comparing the EASA learning objectives with the contents of your books - or just subscribe to one of the Question Banks and make sure that you can answer the questions!
The cost of the books is probably pennies compared to the amount of time it will take you to prepare for and sit the exams so you it would probably be worth investing in some new ones. Unless you have a foreign (ICAO) ATPL you will need to complete an approved course in any case, and that will no doubt have training material associated with it - though I am scratching my head to work out the circumstances in which you would have to retake just those exams when your books date from 20004 ... ?