I tested the smaller version of Kindle a year ago or so - it really did not work too well. Kindle now supports pdf (that was not always so), and memory can probably be upgraded ad infinitum. The real problem is quite stupid, namely that there is no zoom-function. Rotating the page by 90 degrees and thereby displaying half of an A4 page is the best Kindle can do, and that leaves the text still awfully small. Reading text is already uncomfortable, reading a formula with a double superscript is impossible. This is especially frustrating if one third of the page witdh is occupied by margins.