What book would be the best to read, in the sense that it does a good job of giving a broad overview of a variety of science topics?

If you like casual science reading, read "THE SCIENCE CLASS YOU WISH YOU HAD..." - David Eliot Brody, Arnold R. Brody, "OUR FASCINATING EARTH" - PHILIP SEFF & NANCY SEFF, "KILLER GERMS" - ZIMMERMANS, "NATURE'S CURIOSITY SHOP" - ZIMMERMANS, "WHY NOTHING CAN TRAVEL FASTER THAN LIGHT?" - ZIMMERMANS
These books cover a lot of science subjects, and are fairly easy to understand and not crazily complicated. Some of those books are a little old, but you can probably find them in your local library.

Hi Enigma'07

I,m presently working my way through "Magic Universe. The Oxford guide to modern science" by Nigel Calder, for the second time. It covers the whole of science from brain rhythms to the big bang. It can't go into great depth of course but it is very informative nonetheless.

oh Nigel Calder, good author, he wrote many great books on science

Carl Sagans' Cosmos is a very informative book.