Is there a travel guide exist that would cover a number of countries and only list some general information about travelling there? E.g. what are the main attractions (with photos and pictures), and some really basic information about the country. It would make planning much easier if one could just sit on the sofa and flick through a book, look at the pictures and decide on the next destination. Then I would buy a more detailed guide (like Lonelyplanet or Rough Guide etc.)
I only know one book that does exactly what you want. It is from the famous Lonely Planet and is called The Travel Book: A Journey Through every Country in the World. It consists of one or two pages per country and describes the most important facts as well as the major sights as well as sometimes how to get there and any other special information.
Here is the Amazon description of the boo (from Amazon Germany, but the book is in English):
The highly pictorial book features a spread for every country in the world. Images for each country are accompanied by short sections of text highlighting various elements of the country, from hard facts and figures, to more experiential types of information. With the traveller's experience at its heart, this book shows a slice of life in every corner of the globe and all points in between, engaging the reader's senses in an adventure which conjures up the sights, smells, tastes, sounds and feel of our amazing world.
If you want slightly more detailed information about countries, Lonely Planet does overview guides such as South-East Asia on a budget and other similar titles. This way, if you have narrowed down a region you're interested in travelling in then these books contain enough information on each destination to narrow down places of interest and basic information on costs for activities and accommodation. I found this highly useful for planning. Get an old second used book, it will be cheaper and you can still find out what places to go to; the cost information etc you can get in more detail once you buy a country guide on it.
As an alternative to a paper travel guide or book, Awespot might be a good place to start.
It's a collaborative travel guide (as WikiTravel for example) but browsable differently: you can check out pictures at random and explore the world map as you will, so you can compare very rapidly different travel destinations.
Disclaimer: I do work on this website.