Boredom Unbound

As I am writing the subject GRE in English in November, I am in the process of reading those authors or periods I have hitherto neglected. By far my biggest area of weakness is 20th century American lit, although I am not entirely ignorant of it.
Among my weaknesses are some canonical poets, especially Shelley, perhaps the most stereotypically "romantic" poet. In five years as an English student (4 undergrad, 1 MA), I was never required to read him (although I think he is more or less defunct now).
I attempted to read Prometheus Unbound last night, and I must say that after Act I I gave up. I've read some works that would no doubt be classified as "boring" by others (remember the OED), but I haven't had this feeling in a long time; it could very well be that I was not in the right frame of mind. It could also be that Shelley, at least in this work, is loquaciously flowery, to the point where I cannot even understand him at times.
Any thoughts, educated readers? By the way, apart from this, I think I should really read Ozymandias and Adonais (his lyrics are far more readable). Are there other works of his that I should really read, something(s) that would be on a standardized test?
Thanks.