In the 1980s K. Eric Drexler wrote his famous book on nanotechnology 'Engines of Creation' and created a storm of interest in highly advanced diamond based nanomachines, a view of nanotechnology which has been ingrained in the public subconscious ever since. However, speak to any modern day nanoscientist and they will tell you that his work is highly speculative and contains a number of serious holes. Many would be even more dismissive.
In this book, Professor Richard Jones presents a more balanced perspective on the issue. He starts by saying that he does believe advanced tiny machine based nanotechnologies are possible, but that Drexler - with his dry, hard system - is barking up the wrong tree. Here Jones makes the case for, as the title suggests, soft machines, based to some extent on nature, or rather, the principles that nature operates on. The fact is - and one of the reasons there is such an interest in nanoscience - that things work differently when they are small, and we should bare this in mind when making small things, rather than just trying to shrink our 'big world' machines down. Nature is of course the one working example of nanorobots, and it does not work based on scaled down mechanical / electrical engineering principles, but by exploiting physics of the nanoscale - Brownian motion, quantum effects, diffusion, etc, and it can do remarkable things by doing so.
Jones's views are grounded in modern scientific understanding, but unlike many, he has actually tried to address the Drexler view and say why he is sceptical rather than just dismissing it out of hand or ignoring the issue entirely.
If you're a little confused over this dichotomy of views - the optimistic Kurzweil / Drexlerites on one side, and the nay-saying scientists on the other, then this is an ideal book for you. If fact I would recommend this book to both of the above two groups as well. Think that nanorobots are an idiot's fantasy? Read this book. Think that tiny hard nanobots will be living inside us by 2025, and might even escape and eat the whole planet? Read this book.
In summary, if you are interested in reading a balance perspective on the possibility of advanced nanotechnologies, then I recommend this book.