There is probably just one self-help/personal development book that I would recommend unreservedly to anyone and everyone and that's David Allen's Getting Things Done: The Art of Stress-free Productivity
I've tried many ways to organise myself and my time and the only method that I come back to time and time again is set out in this book.
When I work the system effectively my life is so much better organised and nothing drops through the cracks.
I particularly like the way that Allen sets out the principles and the methodology behind his thinking but also sets out very specific and practical steps to getting things organised.
I will come back to Getting Things Done (or "gtd" to those who advocate it) on other occasions but my full and thorough review amounts to BUY THIS BOOK!
ps For those who want a taste of the gtd methodology before buying the book the web is full of sites setting out ways to implement the methodology and people's experience of putting it into practice. Some of my favourites are:
GTD Resource List (someone had some time on their hands...!