A mathematical theory is not to be considered complete until you have made it so clear that you can explain it to the first man whom you meet on the street. (Hilbert)
just now, Lang has published another book on algebraic numbers which, in my opinion, is still worse than the former one. I see a pig broken into a beautiful garden and rooting up all flowers and trees. (Siegel)
Unfortunately, this is the state of modern mathematics. It is getting farther and farther away into senseless abstraction. There are very few true authors who can write clear and readable books on math, that can be understood not just by people who already know the subject well.