17905 Naum Akhiezer/I. Glazman: Theorie der linearen Operatoren im Hilbertraum.
Akademie-Verlag 1954, 370p.

J. Blank/P. Exner/M. Havlicek: Hilbert space operators in quantum
physics. Springer 2008, 660p. Eur 97.

17925 Siegfried Brehmer: Hilberträume und Spektralmaße. Akademie-Verlag 1979, 220p.

Anatolii Dvurecenskii: Gleason's theorem and its applications.
Kluwer 1993, 320p. 0-7923-1990-7. $137. In 1957 Gleason described the quantum 
mechanical states on the closed subspaces of a separable Hilbert space. 

26876 Karl-Heinz Goldhorn/Hans-Peter Heinz/Margarita Kraus: Moderne mathematische
Methoden der Physik II. Springer 2010, 340p. Eur 15 (Ebuch).

Maurin.

W. Mlak: Hilbert spaces and operator. Kluwer 1991, 290p. HFL 240.
An elementary, but very nice introduction to functional analysis for students.

James Retherford: Hilbert space. 
Cambridge UP 1993, 150p. 0-521-42933-1 (pbk). Pds. 14.

17994 Peter Semrl: Maps on matrix and operator algebras.
Jber. DMV 108/2 (2006), 91-103.

5239 Joachim Weidmann: Lineare Operatoren in Hilbertraeumen.
Teubner 1976.

17546 B. Yadav: The invariant subspace problem. EMS Newsletter December 2005, 19-23.
Does every bounded operator on a Hilbert space have a non-trivial invariant
subspace? This question has a positive answer for finite-dimensional and for
non-separable spaces; the problem is unsolved for general separable Hilbert spaces.

16259 Nicholas Young: An introduction to Hilbert space.
Cambridge UP 2004, 230p. $30.