I would recommend that you join your public library, they have a growing selection of books for download over many categories and contain many recently published books and are being added to all the time, for a larger selection of books join several libraries as there are a number of suppliers of E Books, who are contracted by public libraries, and have different lists of books, usually these downloaded books are available to read for 2 to3 weeks.
The one drawback as far as I know is that Kindle format is not supported by Public Libraries and most downloads are in E Pub format and if you try to convert to Kindle format you will be blocked by DRM
It is usually possible to join a library in the area that you are travelling.
Cheers
David