The X Factor winner will release his studio record on October 17, following the release of his first single proper 'Run For Your Life' on October 10.
Speaking to MUZU about his new material, Cardle explained: "The album is actually quite diverse in the sound. We've been working with a few producers, so a lot of the tracks sound different.
"There's some soul stuff, some rocky stuff, there's a lot of stuff that is stripped right down to just guitars and cellos and strings. It's got a bit of everything in there. I'm really proud of it."
The 28-year-old has worked with a range of songwriters on Letters including Take That's Gary Barlow, Robbie Williams collaborator Guy Chambers and Fame Academy winner David Sneddon.
> Matt Cardle debuts new single 'Run For Your Life' music video
Watch the full interview with Matt Cardle below: