which book is good

Actually ,the second one focus to the symbian "OS" information , ARCHITECTURE is the most information . If you intend to programme on the symbian os at frist , the third one is my recommendation .

1) targetted at passing the ASD exam. Good for covering all the basics.

2) Completely irrelevant to developing applications. No need to read this at all.

3) The best book for beginners in my opinions. Make sure you get the 2nd edition.

4) 1st and 2nd editions are out of date. 3rd edition up to date, Has more in it than then others but maybe 3 is easier to learn from. There are only 2 sources of information on the entire planet to get a good overview of descriptors - one is the descriptors blog page (from the author of 5) and the other is this book. The book has more in it than the blog on descriptors if you want a complete reference.

5) Symbian OS explained - good book but not targetted at beginners.

if you want to learn Symbian I think 3) is best to read first and then have 4 or 5 as reference. Note that 5 doesn't have any UI development in it but 4 does which may be important in your choice.