Rakis -
Here's a golden rule:
***PDF's don't look good on the Sony Reader***
This is especially true for Travel Guides with their intricate layout of maps and boxes and sidebars.
I went to the Travelfish site. I can only imagine they would look worse on a Sony than the Lonely Planets guides since the pages are in the larger A4 size. Also, the Travelfish guides seem of little value - out of date, dubious research and only 19 pages long.
If you are really interested in travel guides I suggest you visit the forums that deal with those countries.
http://www.thaivisa.com/forum/ would be a good start.
Folks on those forums would be happy to give you current first hand information about anything and everything you can think of - and also things you would never find in any Lonely Planets/Rough Guide/Travelfish. Download all the advice in html or text and create your own travel guide. Stick THAT on your ebook reader.