Walaikum Salaam,
Brother Ufsir, first I would like to welcome you on this forum.Secondly, I am very glad to see you taking interest in the forum and providing some worthy information to all of us.
Now coming back to the attachment problem, actually we can't have bigger attachments here at the forum. The maximum attachment size for a zip file is around 98 kb. I guess your file is bigger than 98 kb that is the possible reason of the problem.
Now what is the solution?
You can either use
www.megaupload.com or
www.rapidshare.de to attach your file and then you can post a link over here.
Hope it will help, please let me know if you have any problem in the process.I am eagerly waiting for that book.
Regrads,
Satan