While I was editing In the Blood I came across an excellent piece of software called NaturalReader. You can take a look at it here and listen to voice samples. I didn't want to rely on having to have a real person (Mrs R in my case) available to read to me, and doing so would have taken up a lot of my wife's time. I also didn't like the mechanised sound of the free text to speech software I had access to, so I was very pleased to find NaturalReader. I went for a two voice package and chose Acapela's British Peter and Rachel. I listened to all of them several times and thought Peter best suited the tone of my books. Rachel reads research to me whenever my eyes are tired or I just feel like sitting back and listening - especially if the subject I'm researching is a bit heavy going.
The voices are not perfect, and certainly not as good as a professionally read audiobook from Audible.com for example, but they have come a long way. I found I soon warmed to Peter and it didn't take long to tune in to some of his speech oddities. You can also edit the phonetics of words if they're not pronounced as you expect, which is particularly useful for characters' names - an example of which is a French character from The Last Queen of England called Michel Levant. Peter would read that surname all wrong to my ears, so I told the software that whenever it came across that word, it would say it more like 'Leh-von' than 'Leh-vant".
You can also create MP3 files so you can proofread on the go with your iPod, which I don't tend to do because I like to pace the room as I listen, and then jump onto my keyboard, pause the speech and make my changes right there in the Word document as I go. Below is a link to a sample MP3 file I created for the prologue in To the Grave so you can hear Peter as I hear him when I'm running through an audio edit.
I think this part of the process really helps to prepare my books for publication and I'm frequently surprised by how often my ears pick up an error that my eyes have missed, sometimes after several drafts. It's also particularly good for editing dialogue, because when it's read aloud to you, you know straight away whether it sounds natural or clumsy and stilted. The same goes for long, run-on sentences and awkward paragraphs in general.
It's not super-cheap, but it's not that expensive either, and to me it's been worth every penny. I was about to add that you only have to buy it once, regardless of how many books you write. Then I realised I have actually bought it twice because I wrote In the Blood on a PC running Windows, and then I switched to Mac so I could use Scrivener (which wasn't available for the PC then). So I've had to buy NaturalReader twice. But it was still worth it in my opinion. It's fun, too. I just had Peter read this blog post back to me. :o)