2025-12-12. Main Book: Version 1.01, some minor typos. Answer Book: Version A.1.01, lots of typos and corrections on Chapter 1. 

2025-12-12. Main Book: Version 1.02, minor typos. Answer book: Version A.1.02, many typos and corrections on Chapter 2. 

2025-12-26. Main Book: Version 1.03, a few minor typos and language corrections. Answer Book: Version A.1.03, many  typos and corrections on Chapter 3, and equation numbers in the exercises statements matched with the Book. 

2026-01-02. Main Book: Version 1.04; removed former (wrong) Proposition 6.3.10, plus minor correction in a few exercise statements. Answer Book: Version A.1.04; many typos and corrections in Chapters 4, 5, and 6; Exercise 9.1.6 had been using the wrong Proposition, so the argument has been corrected. 

2026-01-13. Main Book: Version 1.05; typo on introduction to weak topologies and minor mistake corrected in the proof of Lemma 12.3.16; a couple of other minor typos.  Answer Book: Version A.1.05; typos and corrections in Chapters 7 and 8. Corrected the proof of Exercise 7.4.6. Changed the statements of Exercises 7.4.7 and 8.3.4. 

2026-01-25. Main Book: Version 1.06; minor changes in the proof of Proposition 9.2.21 to avoid early mention of characters; minor change to Exercise 9.2.16; minor change in Example 9.5.10; minor error in the statement of Exercise 9.6.16; typo in the title of subsection 9.8.2; "selfadjoint" missing in the statement of Exercise 10.2.3; minor change to the statement of Exercise 10.6.25; changed the statement of Exercise 11.5.5; correction in the statement of Exercise 11.5.7; typo in the statement of Proposition 11.6.3; minor change in the first paragraph of Chapter 12; corrected Remark 12.1.14; minor change in the statement of Exercise 12.7.3; clarified statement of Exercise 12.7.10; improved statement of Exercise 13.2.13 and included mention of this in the proof of Theorem 13.2.15; added Exercise 12.1.23; removed Exercise 13.2.27 (duplicate of 13.2.21); moved Exercise 13.4.2 to Section 13.1 where it belongs; added local table of contents to section 13.4; added mention of sot in Exercise 13.4.13; minor change of notation in Exercise 13.4.19; corrected Exercise 13.4.24.   Answer Book: Version A.1.06; solved equation numbering issues; many typos and corrections in Chapters 9-13; changed the answer to Exercises 13.2.32 and 13.4.23. 

2026-02-01. Main Book: Version 1.07; mistake in the statement of Exercise 10.5.16; included new Exercise 12.1.24; changed the statement of Exercise 14.2.8; slightly changed the statement of Corollary 14.2.18; clarified the statement of Exercise 14.2.19; exchanged Exercises 14.3.2 and 14.3.4, as the former needs the latter; clarified the statement of Exercise 14.3.3; clarified statement of Exercise 14.5.2; made Lemma 14.5.22 into a Proposition and clarified the statement; added Exercise 14.5.13; added a new Exercise B.3.1 to correct Remark B.3.2 (it was circular) and to help with what now is Exercise B.3.2; clarified the statement of Exercise F.0.11; corrected Exercise F.0.13. Answer Book: Version A.1.07; many typos and corrections in Chapter 14 and the Appendices; changed the answer of Exercises 14.2.8 and F.0.12.


2026-06-09. Main Book: Version 1.08; missing hypothesis T in B(H) in Exercise 10.6.9; added Exercises 7.5.25 and 7.5.26 to extend Theorem 7.5.12 to the span of any n+1 points; removed T from last paragraph of the proof of Proposition 9.6.2; three typos in the paragraph after Corollary 9.6.14; rewrote Example 9.7.19; after Proposition 10.5.5, added mention of the fact that the result fails for non-selfadjoint idempotents; before Propositon 10.3.6, corrected wrong internal reference about the Volterra operator; typo after Definition 11.1.8; minor rewriting paragraph before 11.3.2; added Exercise 11.3.10. 

2026-07-31. Main Book: Version 1.09. Typos in the limits at the beginning of subsection 2.5.2. Minor rewrite of Definition 4.3.10, and corrected notation mistakes in the proof of Lemma 4.3.11. Clarification in the comment after Lemma 4.3.11. Removed the unneeded closure on Proposition 10.2.3, and added mention of Exercise 7.5.27. Added Exercise 13.4.28 and mention of it after Proposition 13.4.33. Typo in the definition of the 2-norm (page 1086). Minor typo and correction in the proof of Proposition 14.7.10. Changed some page references to subsection references.