Kindle is not the only ereader to have an eink screen, in fact every device that is marketed as ereader (and not i.e. a more generic tablet) uses this technology.
Said that, basically every ereader available today can do the things that you need; I think that the real choice when speaking about scientific books that contain math and formulas is about the ebook format, not about the ereader: reflowable text formats like Amazon's
.azw and everyone else's
.epub can get the job done, but maybe for some more complex layouts, a fixed page format like
.pdf could be a better choice. It really depends on the specific book and how well is formatted.
Choosing an ereader and a brand is more a choice of an ecosystem rather than about differences in the hardware (all of them, more or less, are equivalent and have the same features); Amazon Kindle is maybe the more closed platform, meaning that it uses its own file formats, while the rest of the world uses the de facto standard
You can also try to have a look at these questions: