I have never read any Cliffs Notes books before; I made it all the way through college either reading the texts assigned completely or not at all. I therefore cannot judge the book as a member of a series, which might conceivably make a difference.
Unlike some critics, Allen is an unabashed fan, if not an overenthusiastic one. He covers some of Asimov’s novels, giving a summary of the plots and analyses. In keeping with the series as a whole, this is intended to be a supplement helping the student learn the material. Inside the front cover is a strong disclaimer warning the student not to depend on the notes instead of the actual books they cover. Doubtless many students ignore the warning.
Everything comes in for positive comment. Asimov’s characters are said to be only sketched in, true, but brilliantly sketched in. And so on.
The book suffers from the fact that in its scant hundred pages, it only covers the original three Foundation books, the three Empire novels, The End of Eternity, and The Gods Themselves. The original Foundation books are covered in fourteen pages; The Stars, Like Dust gets twelve. Given the relative strength of the former and weakness of the latter, this seems odd. And, of course, anything to do with robots is left out. No The Caves of Steel, for instance.
Allen’s synopses are good, and his analyses are good, too. The issue is that he gives too little space to what deserves more and too little space to what deserves less.