If I understand the documentation of the AMS classes correctly, then a theorem in the style "plain" should have bold heading and italic body text, in the style "definition", there should be bold heading and normal body text, and in "remark", there should be an italic heading and normal body text. This is described her in section 4: http://www-math.mit.edu/~psh/amshelp/2.2/amshelp.pdf
Here, with amsbook, all headings look the same (in small caps), and there is no distinction between "definition" and remark in the body text.
Example:
\documentclass{amsbook} \theoremstyle{plain} \newtheorem{thm}{Theorem} \theoremstyle{definition} \newtheorem{dfn}{Definition} \theoremstyle{remark} \newtheorem{rmk}{Remark} \begin{document} \begin{thm} Here comes a theorem. \end{thm} \begin{dfn} Here comes a definition. \end{dfn} \begin{rmk} Here comes a remark. \end{rmk} \end{document}
Is this behaviour correct or is there a problem in my LaTeX environment? I did not find any remarks in the documentation about a different behaviour for amsbook (then for, say, amsart). I also remember that, using an older version of TeXLive, the look of the headings was dependent on whether hyperref was loaded or not.
amsbook
class changes the theorem styles to suit the general setup of the class. In particular, all theorem headings are in "caps and small caps".amsbook.cls
(class) theorem styles andamsthm.sty
(package) theorem styles. The ones you describe are the ones ofamsthm
and not ofamsbook
.