This is a text that I enjoy very much. Either the first or second edition is well-worth study. However, I note, the textbook does seem a bit rushed. However, the more I revisit the book, the better it gets !<br>(1) Read: "the probabilistic interpretation of quantum mechanics was controversial from the beginning, to the present there continues to be a tension between the probabilistic interpretation and the deterministic evolution of the wave function." (page 30). That  line concludes chapter one, historical introduction. Read of Max Born and Pascual Jordan's  "mathematically fallacious derivation" (page 20) and dark energy, too (page 24). The third exercise here is interesting: "suppose the photon had three polarization states, rather than two. What difference would that make in the relations between Einstein's A and B coefficients ?" That is a very good question !<br>(2) Solutions to Schrodinger equation precedes a general discussion of 'general principles of quantum mechanics.' So, what is here, chapter two, is a crash-course in Hydrogen atom, harmonic oscillator, central potentials. In effect, a recapitulation of solutions of differential equations by special functions. Happily, harmonic oscillator is re-introduced later (page 149), by way of symmetry. Exercise two is of some interest: "derive a formula for the rate of single-photon emission from the 2p to the 1s state of Hydrogen." Student exercises placed at the end-of-chapter.<br>(3) Third up, General Principles. Here, the text gets interesting. Regrettably, Dirac's 'Bra-Ket' notation is mentioned only in passing. Weinberg writes: "The notation we use is commonly used by mathematicians." (page 60). It is an easy exercise (and I do it) to translate Weinberg's notation into Dirac's Bra-Ket notation (for instance, equations 3.1.16 and 3.1.17, page 60). An interesting discussion of delta-functions, that is, distributions follows. If you cannot instantly derive equation #3.2.22, page 64, then, no need to continue further until such is accomplished ! Symmetries introduced in section 3.4. Weinberg writes: "much of this can be learned from fundamental principles of symmetry, without recourse to classical mechanics." (page 74). Dyadic notation does not resonate with me (page 71). Third chapter concludes with this: ".. that today there is no interpretation of quantum mechanics that does not have serious flaws...in my view, we ought to take seriously the possibility of finding some more satisfactory other theory." (page 102).<br>(4) Regards spin: " this internal angular momentum came to be called the electron's spin...at first this idea was widely disbelieved." (page 104). Then, read: "There is nothing about spin that requires relativity to be taken into account, and nothing about relativity that requires elementary particles to have spin one-half." (page 106). Now, think about that ! Why ? Because that is something that is very often obfuscated ! This is a lucid discussion of fundamentals. Discussion of Stern-Gerlach is brief, yet insightful (page 116). Internal Symmetries: "leaving spacetime coordinates unaffected." gets further elaboration (pages 141-150).<br>What we learn of rigid-rotator model is excellent companion to the discussion in Arno Bohm's text (1979, chapter three). The problem sets vary in difficulty: "A particle of isospin one decays into an anti-Kaon and a Kaon. Assume that isospin is conserved in the decay. What is the ratio of the rates of decay processes..." (page 168). We met the Kaon previously in a discussion of invariance under space-inversion (page 153). Note, not every exercise is difficult: exercise #2, page 167, is merely a derivation of a vector-identity.<br>(5) Broken Symmetry (section 5.8) is discussed. Here, meet the Ammonia molecule. This is an interesting discussion. For another physical description, turn to The Feynman Lectures (Volume 3, 8-11). Weinberg:<br> "a general feature of spontaneous symmetry breaking... it is always associated with systems that in some sense are very large." (page 207).<br>(6) Fluctuations (section 6.5): an exceptional discussion. You get it more than once. Here, one derivation (pages 222-224)  and a more accurate derivation later (final chapter, pages 380-387). That is surely good pedagogy ! That is, a multi-pronged approach. That multi-staged approach is utilized in the discussion of  density matrix: introduced on page 72, discussed later for open systems (page 237). That spiral approach comes in handy when Weinberg mentions probability: First introduced section 1.5 (pages 24-30), then, an elaboration when discussing multiple scattering (page 257) and charged-particles (page 350). Weinberg is always reiterating conservation of probability (which, by the way, is both explicitly and implicitly emphasized).<br>(7) Weinberg, on Lagrangians: "The great advantage of the Lagrangian formalism is that it provides a simple connection between symmetry principles and the existence of conserved quantities." (page 327). From there to Hamilton, then constraints. The section on constrained Hamiltonian systems is exceptional. Read: " Dirac's assumption yields the same equations of motion as provided by the classical Lagrangian for this model." Then, an excursion into Feynman path integrals. That excursion concludes the chapter. What is here on path integrals is brief, Shankar will provide more (1994). Weinberg:  "...there is a troubling weirdness about quantum mechanics, perhaps its weirdest feature is entanglement." Regarding end-of-chapter problem sets, many are quite challenging. Exercises are comparable to Merzbacher's text.<br>(8) Bringing my personal view to an end: I note the exposition is terse (contrast Shankar or Merzbacher).<br>Footnotes are instructive, examples: Born, Heisenberg, Jordan upgraded from one to three-dimensions (page 23), factorization and symmetry (page 38), infinite-dimensional proof (page 67), Dirac and holes (pages 84 and 153) and considerations of spacetime symmetry (page 132). The text is aimed at graduate level, so you had better know prerequisites (say, Griffiths). Mark Srednicki writes "text is...for those who have had a good undergraduate introduction." (Physics Today). That prerequisite is necessary, but, likely insufficient !  I feel the text works best as a prelude to Weinberg's  marvelous textbooks of Quantum Field Theory. The preface: "... numerous examples from elementary particle physics."<br>There is much to learn in Steven Weinberg's lectures.