I'd like to recommend the "Fu Manchu" stories of Sax Rohmer. Horribly "non PC" by modern standards, I'm afraid, but the most
wonderful adventure stories.
In case anyone's unfamiliar with them, these stories involve the adventures of the British secret agent Nayland Smith, and his "sidekick", Dr. Petrie, in attempting to foil the sinister plots of a Chinese master criminal, Dr. Fu-Manchu, to take over the world.
There are three books in the series which are currently available electronically, which I've collected together into an anthology called the "Sax Rohmer Anthology, Vol 1". Available for both the Sony Reader and in MobiPocket formats from the book uploads forum.
The reason I'm recommending them is that I've just finished re-reading them myself, and I'd forgotten just how good they are. I've just uploaded new versions which correct all the typos I spotted while reading them.
Please do let me know what you think if you read them. I think they are just THE most wonderful stories.
The Sony Reader version is
here, the MobiPocket version
here.