I really like these "DK Eyewitness" travel guides. I always buy one for the country/city I am going to visit. They provide interesting and practical facts about sightseeing, using the local public transport or driving, getting to/from airports, eating out, going out, shopping, hotels, useful maps of city centres, health and safety tips, some background history, etc.
The translations (and pronunciation guide) of common phrases in the local language are useful but limited.
Lots of pictures make the book more interesting in itself and makes for a nice bookshelf souvenir afterwards.
Another great thing about the Eyewitness travel guide series is that the books are always laid out in the same way. So once you start using them, you'll always know what information you can find and where it will be in any other Eyewitness guide book.
A slight drawback is that the books are medium-size and can weigh from 500-800 grams (depending on which city/country the book is for), and the paperback versions always get a bit dog-eared being carried around in my day-pack. However, the "Top 10" format (where available) is a cut-down version that is much smaller, lighter, easier to carry and very, very convenient. However, the downside is only limited information with much less detail is provided. So if you are only staying for a few days this is OK, but for longer stays the full version is better.
To paraphrase and old credit card ad: "Don't leave home without it".