Which Rick Steeves Book

Definitely. And you don't need to take the whole book with you. Tear out the chapters you will need from each book and binder clip them together. Saves space and weight in your bags.

The country and city books go into much greater detail than the Best of Europe book.

If the B of E book does not list enough things to keep you occupied for your ( unspecified) amount of time in Europe, then individual books may be helpful.

I would recommend that you download the books to you iPhone or iPad, this way you can access which ever book you want without adding weight to your bag.

It depends. Which countries are you going to, how long will you be in each country, and which places in the countries are you visiting?

Also note that in addition to the Best of Europe book and the individual country books, there are city books. These have more information such as museum tours, shopping tips, travel with children tips, etc. Again, whether you should buy more books, and which ones, all depends on how long you're going and what you'll be doing.

As mentioned earlier, it depends on where you're going and how long you plan to stay in each destination. I like to borrow the Rick Steves country books from the public library when I'm in the planning stages, make some appropriate notes for myself, and then if we're staying 3 or 4 nights or more in one major city (or likely to return to that city on another trip), I'll buy the city books (i.e. London, Barcelona, Rome). I like the compact size of the city books and the walking tour maps.

I think guide books are a great value for a small investment in a trip worth thousands!

It would depend on where you are going some cities have their own book so they would be a good buy as the Best of book will just have an overview of the cities. Which countries are you visiting?

I keep all guidebooks on my iPad.

You can also decide if you want to buy the ebook when you arrive in that city/country.

I agree with previous posters-buy the books. Minimal investment considering your overall cost and a great deal for what you get. I'm a week away from Heart of Portugal and re-reading the book I'm again astounded at the valuable detail. I'll be tearing out the sections I need (I can hear the books are sacred crowd gnashing their teeth) as the bulk is just too much. And we are doing back to back tours so I'll be doing the same with the London book if I can get to it. I tried the e-versions and, while nice for just reading, for touring I like to have the relevant paper sections with us for the day, then toss them. I use the rip and staple method-looks like hell, works for me. I don't like pulling out an iPad or e-reader while touring. I often buy other than RS guide books just to compare and I can't seem to learn my lesson. I have another for Portugal and it's just meh.

So far, your previous posts have only mentioned visiting London, Paris, Venice, and Rome. If that's the focus, then I would have selected the four separate city guides. However, Best of Europe covers them all adequately, as well as perhaps something else on your list, like the Berner Oberland in Switzerland.