That this observing guide has survived into its fourth edition is testament to its quality. Clearly one of the best companions to practical astronomy, for all levels of interest (including simple naked-eye observing). It is in the usual format, based around monthly star charts for both northern and southern hemispheres, and then more detailed constellation and lunar maps with their accompanying text briefly describing the most interesting objects. The depth of coverage is surprisingly high, so the book is really inexhaustible. I had the second edition, and it was an inspiring guide when I was first learning the sky. But it has proved to be a permanent companion, even after going on to more detailed atlases and observing handbooks, since no single book matches its convenience and beauty for casual stargazing.
Another section gives a good introduction to the science of astronomy - particularly as it relates to the universe which a backyard amateur sees! On the other hand Ian Ridpath's accounts of constellation mythology and lore are especially insightful, and he explains many more star names than other similar books do.
I definitely found the new edition worth buying, mainly for the improved star charts - they give much higher contrast between stars and background in both low light and red light. Don't be deceived by the relatively 'washed out' appearance of the background in full daylight! Even then, there is a beauty to these charts that grows on you. (The addition of colour to the brightest stars in the monthly charts is another beautiful touch.) The text is generally just a little bit improved and updated. It is probably for the best that the five-year planetary finder charts are removed to a companion website - not enough years' worth can be included to match the life of the book - although I think they CAN still be useful as an illustration of the type and SCALE of motion of each planet across the sky.
P.S. Just a note on using the monthly charts. They are cleverly drawn (taking advantage of being split across two pages) to give a very realistic sky-view - without the distortion of normal one-sided planispheres. To make good use of them instead of a planishere, though, you need to remember that the 12 charts also represent the sky through a single day, moving FORWARD at two-hour intervals. So the September chart shows the sky at 10 p.m. on the 15th: for midnight on the same day go to the October chart, for 8 p.m. go to the August chart. This wasn't explained in the book, and it took me ages to cotton on! (It's a pity that the charts weren't put into separate blocks for each hemisphere, to make it easier to flick between the months for an animated sky view!)