This volume is a selection of invaluable papers by P-G de Gennes -- 1991 Nobel Prize winner in Physics -- which have had a long-lasting impact on our understanding of condensed matter. Important ideas on polymers, liquid crystals and interfaces are described. The author has added some afterthoughts to the main papers (explaining their successes or weaknesses), and some current views on each special problem. The text is simple and easy to read.
Do not be deceived by the title. This book is heavy going. The "simple" refers to the fact that PGG's approach is to derive scaling laws that paint "the big picture" rather than trying for a detailed picture with complex equations that often need numerical solutions. It could also be argued that the title is a kind of humblebragging. In my opinion, you're unlikely to enjoy this unless you have a PhD in the relevant physics. If you do have the right education, you can marvel at the depth of his insights that covered a wide range of topics. I once saw him at a conference. He was supposed to talk about rubber elasticity, but since an expert was also giving a talk on that subject, PGG decided to improvise a talk on the growth of plants instead... A rock star scientist.