The intention of this review is to give the reader enough information to decide whether or not to read this book.  That Feynman was perhaps the foremost physicist of the middle of the 20th century goes without saying.  He was also a great educator and popularize of the most complex ideas of classical and modern physics.  All well and good, but what about this book?<br><br>In short -- I enjoyed this book, but thought that it was a bit unfocused.  This was due to the fact that the book was taken from his three-volume lecture series on physics, which was prepared from his lectures to undergraduates of Cal Tech in the early 60's.  The editors chose what they considered to be the six easiest lectures and put them in a single small volume, as contrasted to the three much larger volumes that make up the whole series of lectures.  The lectures included in the book were not consecutive lectures from the whole series, so there was a bit of a continuity problem with the flow of the text.  Also, because so much has been left out from the complete lecture series, the subjects that are covered are done so in a very fragmentary manner.  Read this book to get a flavor for Feynman as a teacher, but not to get a complete picture of any of the subjects that are covered.  While I liked the book, I liked Feynman's "The Character of Physical Law" even more.  It was also based on a series of lectures (covering some of the same material), but all of the lectures in that series were provided and as a result the book was more focused and self contained.  I recommend both books, but if you only want to read one, I would recommend "The Character of Physical Law".  Both give a flavor of Feynman's teaching style and they are making me consider buying the full three volume lecture series, even though the list price for the three books (plus a volume on problem solving) is almost $200.<br><br>In more detail -- The lectures covered in this small book are:<br>--- Atoms in motion - Very general overview of atoms, molecules and their relation to vapor pressure, melting and solidification.  Very general and very elementary.  Well suited for a high school student.<br>--- Basic Physics - Very general overview of the scientific method, classical and modern physics.  Also very general and suitable for a high school student.<br>--- The Relation of Physics to Other Sciences - Here, in my opinion, Feynman digresses quite a bit, throwing in a bit of chemistry (including the Krebs cycle) and a bit of biology (including DNA).  This chapter is suitable for an advanced high school student or undergraduate college student.<br>--- Conservation of Energy - These last three chapters start the meat of the book, focusing of basic physics topics.  The conservation of energy is taught from a simple analogy of the conservation of children's blocks.  He follows the same approach he used to describe the first law of thermodynamics; using the concept of reversible machines being the most efficient possible to derive the law of conservation of energy. If one assumes the law of the conservation of energy one can prove that a reversible machine will be as efficient as possible, so both are statements of the same thing.  I knew this approach from a study of thermodynamics and while not stated as such, Feynman allowed me to see that the concepts of reversibility and the conservation law are not only the same thing but that they are much more general than just applying to thermodynamics This alone was worth the price of the book.  It illustrates the power of his teaching style.<br>--- The Theory of Gravitation - I was disappointed with this chapter.  Instead of following Newton's thinking he states Newton's law of gravitation at the beginning of the chapter and then mentioned that it came directly for Keppler's second and third law.  I was hoping for more.  This chapter illustrates the difficulty in choosing just a chapter from a larger work.  These ideas are developed more completely in the complete lecture series (there is also a separate book containing Feynman's lost lecture on this subject).  On the plus side, there was an excellent discussion of why there are two tides pre day, not just one.  Feynman, corrects the off stated idea that the second tide is due to the moon pulling on the earth.  Again, in my opinion, this discussion is also worth the price of the book.<br>--- Quantum Behavior - This is taught from the standpoint of the two-slit interference experiment with photons and electrons.  This touches the heart of quantum behavior, but just touches it.  Again there is much, much more in the complete set of lectures.<br><br>All in all --  Some of the lectures were a bit too easy.  The choice of only 6 easy lectures from a three-volume set of lectures made the text somewhat unfocused.  Some of the lectures were very incomplete, but they are all pure Feynman.  Feynman makes physics exciting (or at least interesting) and provides information to readers of all backgrounds.  I recommend this book to high school students, first year college students and teachers.  Those with a more advanced physics background may find this book a bit too basic, but they may see new ways of looking at things.  I also recommend Feynman's "The Character of Physical Law", which covers some of the same material, but in a somewhat more focused manner.  In fact I liked it more than this book.  I gave it five stars and this book only four.