@ On page 6, in the first display both instances of fancy script \B should be plain B (it’s a single block, not the collection of all blocks); and on page 7, part (i) of Theorem 1.21 should have n = k − λ a square, not k.

@ On page 11, the reference to (1.7) preceding the statement of Proposition 1.33 should be to (1.8); Proposition 1.34 should really be Hughes’ 1961 result that n is in {2,4,10}, because we do not yet know that n=4 works, and will not prove that n=10 doesn’t occur.

@ The intersection triangle on page 87 for this Steiner system (Table 6.1) should have 3,2,3 in the middle of the bottom row, not 2,3,2.

@ Not an error, but an unfortunate bit of notation: in the proof of Proposition 1.48 on page 18, please change n_i to N_i to avoid the ugly n_n.

@ On page 21, the next-to-last line should have “in accordance with (1.52)”, not (1.42). [Noted by Nathan Kaplan, who also lists a few apparent typos in chapters 4 and 5, which we won’t cover in this class.]