typos:
Page 2 line 2: 'we denote it by' should be 'we denote by'
Page 5 line -6: comma after definitions.
Page 13 line 3: 'representations' should be 'representation'.
Page 19 line 16: Remove the comma after 5.3.3.
Page 24 line -8: 'decomposition' should be 'decomposing'.
Page 26 line -5: Replace 'simple characters' by 'simple representations'. At the end of the paragraph insert an extra sentence: 'As a matter of terminology, if a representation $\rho$ has character $\chi$, we define the kernel of $\chi$ to be the kernel of $\rho$.'
Page 42 line 15: The first sentence of Theorem 3.5.1 should be: 'Let $S$ be a commutative ring with a $1$ and let $R$ be a subring (containing $1$).'
Page 66 line -4: V should be W (three times).
Page 66 lines -2 and -3: W should be V (three times).
Page 107 line 15: the left side of the equation should be
\sum_{r\ge 0} \dim ((IG)^r/ (IG)^{r+1})t^r
Page 124 line 4 (in the proof of 7.3.2(2)): With the hypotheses of 7.3.2 it is not true that $U/\Rad U$ is semisimple (this is true in restricted circumstances, such as for modules over a finite dimensional algebra). From line 3 onwards, replace 'The bottom arrow is an essential epimorphism' to the end of the paragraph by
'The bottom arrow $\phi:U / \Rad U \to V/\Rad V$ is an essential epimorphism if and only if it is an isomorphism. We prove that the first statement implies the second. Suppose $\phi$ is an essential epimorphism and let $M$ be a maximal submodule of $U / \Rad U$. Then $\phi(M)\ne V/\Rad V$, and so the induced map $(U / \Rad U)/M \to ( V/\Rad V)/\phi(M)$ is nonzero. Its domain is a simple module, so the induced map is one to one. It follows that the kernel of $\phi$ is contained in $M$. Thus $\ker\phi$ is contained in every maximal submodule of $U/\Rad U$, and hence in their intersection, so it is zero. Because $\phi$ is both one to one and onto, it is an isomorphism.'
Page 126 line 6: Replace the sentence by:
'We define idempotents $e_i\in A/I^i$ inductively, starting with $e_1=e$. For $i\ge 2$ the element $e_i+ I^{i-1}/I^i \in (A/I^i)/(I^{i-1}/I^i)$ will correspond to $e_{i-1}\in A/I^{i-1}$ under the isomorphism given by the third isomorphism theorem.'
Page 128 line 2: The final = before the symbol S should be an isomorphism sign. This isomorphism could also be explained.
Page 136 line 1: '6.12' should be 'Corollary 6.3.7'
Page 136 line 2: '7.14' should be 'Theorem 7.3.9'; '7.13 and 6.3' should be 'Theorem 7.3.9 and Proposition 6.2.1'
Page 136 line 9: '4.12' should be '4.3.7 and Corollary 4.3.8'
Page 137 line 7: '4.13' should be '4.3.8'
Page 138 line -10: '6.4' should be '6.2.2'
Page 138 line -6: '7.14' should be 'Theorem 7.3.9'
Page 139 line -7: '6.2' should be '6.1.2'
Page 139 line -6: Delete '\cdot kH' from the right of the equation. (The deleted symbols are correct, but unnecessary and confusing.)
Page 140 line -10: Delete 'in 4.9 and'
Page 143 line 7: '4.13' should be 'Corollary 4.3.8'
Page 143 line -4: '6.2' should be 'Theorem 6.1.2'
Page 144 line -13: '11.8' should be '11.2.1'
Page 182 line18: 'degree is divisible' should be 'degree divisible'
Page 209 line -1 and following: Probably Ua and Ub should be U_a and U_b. This would look better in the diagrams on page 210, but at least the notation is consistent.
Page 210 line 6: D_{20} should be D_{30}
Page 211 line 8: 'module' should be 'modulo'.
Page 227 line 15: the final 'RG-module' should be 'RH-module'.
Page 308 line 19: 'orthogonal' should be 'orthogonality'.
Page 312 lines 4 and -7: on both lines 'Lemma 5.5' should be 'Proposition 5.2.3 or Example 5.2.4'.