Good LaTeX template for book about maths

i would suggest using the amsbook document class. it incorporates amsthm and amsmath, and is tuned particularly for use with math-heavy books. several publishers other than the ams (american math society) base their house packages on amsbook.

for variations in the final appearance (while using exactly the same input), there are several ams "author packages" that format the output in the specified style of the different ams book series. all are extensions to amsbook, guaranteeing consistency of input handling and the ability to switch smoothly from one style to another if desired.

there are some differences between amsbook and the basic latex book class, principally in the input style of the top matter and in the inclusion of starred chapter and section titles in the table of contents; these are "house style" matters based on traditional ams practices. these decisions are subjective; your mileage may vary.

amsbook is part of the amscls collection (formerly ams-latex), which is included in the latex "required" components. all are on ctan and in the tex live distribution.

disclaimer: before my retirement, i was one of the maintainers of the ams-latex collection, and principal support contact when ams authors encountered problems.

Your question seems a little fuzzy: Readability? Good looks? That's in the eye of the beholder. Likewise, there usually isn't much to a template. It sets up the basic structure of the files that you will input into it (such as the chapters). Since you indicate your book is in Analysis, you should use the amsbook format. TUG (TeX User's Group) has a AMS book template that can get you started. The AMS (American Mathematical Society) has more in depth information to help authors prepare there books in the style of the AMS here. The link to author monograph packages might be especially helpful.

You should also be aware that most schools with math programs (at least in the US) have LaTeX templates to fit their style: example. Likewise, many book publishers have their LaTeX templates: Springer.

The AMS book template link I provided is fairly basic, but since you are talking about readability, it sounds like you are looking for more than basic. If that's so, consider a math book you like the typesetting on and check the website for their style files.

Here is the free available algebra book from Jim Hefferon: http://joshua.smcvt.edu/linalg.html/ You can download the sources and have a look into the preamble of the document. You can get some ideas or use it as a skeleton for your book.