If your budget runs to £150 you'd be be better off with a tablet running Aldiko or Moon+. The only reasons to get an ebook reader these days is because they're substantially cheaper than a tablet (like <£50) or you MUST have long battery life.
My ebook reader cost £109. A lot of people prefer reading on ebook readers because of the screen. Many like myself find that they get eye strain after reading on an LCD display for long periods. I find it much more comfortable to read on eink screens. I also would spend £150 on a tablet.