You are proposing a long journey through multiple countries. Personally, I always buy DK Eyewitness guides for each country, because they are superb for travellers who like to create their own personal route preference using the regional photos, architectural diagrams, and city highlight walking routes. I love their their concise "must see" lists, and cherry pick what appeals to me.
I hang on to the guides and paper maps as they are a reminder of those travels many years later.