I don't think there's such a thing as "cheating" when mustering learning strategies, only whether or not what you're doing is conductive to your learning.
My answer probably depends on your level, which I don't know. If you are having so much trouble that you can't do it without that crutch, then maybe — but then again maybe you should be trying easier texts first. If on the other hand you're just fine, and are just trying to get ahead faster, remember that there's the twin danger of, one the one hand, failing to prepare yourself for other texts, which when read out of the blue won't give you the benefit of telling beforehand what they are about, and on the other hand the problem of self-confirmation:
My grandmother told me once a story about a Latin exam about Caesar. Obviously Caesar would always win in De Bello Gallico, so she had no reason to suspect that this wasn't the case. Of course, or else this wouldn't be a story, in this particular case Caesar had lost the battle, and she failed the exam.