I'd like to hear opinions from those who have already some experience on Quantum Field theory, what do they think of Weinberg's 3 volumes, whether they are so hard compared to other books or not. It happens that I have been reading some books on QFT, the last being Ryder's book from 1996. I had an excellent experience with Weinberg in Special/General Relativity, and found no major problems while reading his book. However, after many readings, I was able to understand only the first ~ 50 pages of his 1 volume on QFT. So, is it more likely that I have not the minimum knowledge required to understand the book content, or is it that those three books are really hard to go through?