Donald Hamilton's Matt Helm Series, although only then first 14 are available as ebooks. Do not equate the books with the movies.
http://en.wikipedia.org/wiki/Matt_Helm
Douglas Reeman's, writing as Alexander Kent Richard Bolito Series. If you liked Hornblower you will like these.
http://en.wikipedia.org/wiki/The_Bolitho_novels
Stephen J. Cannell's Shane Scully Series is good too.
http://en.wikipedia.org/wiki/Shane_Scully
Apache