You say that Liang's textbooks are not good, because almost all the textbooks in China are written according to Liang. This can be said to be the most classic textbook in China. As for the supporting ppt, this is all added by the university teachers themselves. If you want to see high-end mathematical methods, you can read "Methods of Mathematical Physics" by Courant and Hilbert, but there is no ppt. What's the big difference between ppt and pdf?