Not sure about that, the Kindle Fire seems to be a tablet (back-illuminated lcd) rather than e-ink, so you won't be able to use it in daylight, like outdoors.
There are lots of good tablets from around GBP60, which can be used as ereaders using Moon+ or whatever. Publications can be downloaded using android apps or direct from relevant sites like gutenberg as epubs, pdf etc.
So unless you particularly want Kindle, there are plenty of alternatives to choose from.
I use a Kobo (similar to b+w e-ink Kindle) for reading books, plus a tablet from Amazon for browsing, downloading Kobo books using their app onto the tablet (the Kobo syncs automatically) and non-Kobo books which I stuff into the Kobo through the micro sd slot.
Maps can be viewed easily on tablets, they can be slid around and zoomed with finger strokes and pinches. For example marinetraffic dot com is a real joy to use via their tablet app, worlds better than direct site.