Best of current cloak and dagger; Blood Royal, by Arden Winch. New York: The Viking Press. 258 pp. $14.95.; The President's Man, by Nicholas Guild. New York: St. Martin's Press. 295 pp. The Man from St. Petersburg, by Ken Follett. New York: William Morrow & Co. 324 pp. $14.; Stalking Point, by Duncan Kyle. New York: St. Martin's Press. 288 pp. $10.95.; River of Death, by Alistair MacLean. New York: Doubleday & Co. 240 pp. $14.95 .; The Midas Touch, by Walter Winward. New York: Simon & Schuster. 334 pp. $15. 50.

For suspense/adventure buffs, there's a mixed bag of books spanning three continents, two world wars, and a potential third. One firmly established writer has produced a minor disappointment, but five others have come up with some intriguing reading.

Blood Royal received publicity in Britain when it became known that both the British version of the book and the BBC film made from it had to be changed to satisfy British security. The novel deals with the kidnapping of a young prince by terrorists and the efforts of an anti-terrorist squad to find and rescue the lad. Its author, Arden Winch, has over 100 dramas for television to his credit, and this, his first novel, focuses on action rather than in-depth character study.

For those who prefer their thrillers set against the backdrop of the American political scene, The President's Man offers more than a modicum of suspense. The plot revolves around the discovery by the director of the CIA that a close presidential adviser may, in fact, be a Soviet agent. Author Nicholas Guild skillfully leads the reader on - one gradually feels that something is wrong without really knowing what. The tension builds with the dual questions: Are the suspicions really true? And, if so, what can one do about it?

Ken Follett's latest, The Man from St. Petersburg, may put some readers off by its explicit and frequent sex scenes, but readers who can get past them will find an intriguing story as well. It is 1914, and European tensions are rapidly increasing. England, fearful of war with Germany, seeks a treaty with Russia, which has sent young Prince Aleksey Andreyevich Orlov to negotiate. Also on the scene: the ''man'' himself - an anarchist who plans to assassinate the prince; the assassin's ex-lover, who is now the wife of an earl; and her debutante daughter, who, rebelling against the general ignorance in which genteel young ladies were kept, finds herself attracted to the handsome and captivating foreigner who respects her intelligence. Follett specializes in realistic novels and characters, and while ''The Man from St. Petersburg'' may not be as strong as his ''Eye of the Needle,'' it is still well done. Of special interest to those who like to have all loose ends tied up is the epilogue, which considerately does just that.

If you're a World War II buff, you may enjoy Duncan Kyle's Stalking Point. A young German World War I flier court-martialed for cowardice eventually finds his way to America, where, under a new identity he builds a new life. A decade later, serving as a pilot for a top-secret project, he finds his past catching up with him as a chance remark on the radio leads to contact with the German consulate, blackmail, and involvement in a plot to assassinate Roosevelt and Churchill. It remains for his wife and his best friend to try to stop him on a breakneck cross-country air race.

For those who remember ''The Guns of Navarone'' fondly whenever Alistair MacLean's name is mentioned, his latest book will be a disappointment. River of Death is by no means his best work. One would think a novel combining Nazi war criminals, booty, a Brazilian jungle manhunt, and a hero with all the derring-do of Indiana Jones (from ''Raiders of the Lost Ark'') couldn't help but be a thriller. But the carefully crafted suspense and taut excitement that has characterized so many of MacLean's previous works is curiously lacking here, and the book provides only a pale imitation of his vintage material.

But World War II adventure buffs needn't lose heart. There's another work that will appeal. Walter Winward's The Midas Touch is a classic espionage/adventure story. The year is 1943. The Nazis have captured Europe's most powerful supplier of war materiel -- a Swedish-based industrialist -- and his beautiful niece. The two are being held in a major center of German arms production, which is the target of an imminent American air attack. It is up to a British intelligence veteran and an American major to rescue them before the air strike.

Billed as a work of fiction, ''The Midas Touch'' mixes enough fact to leave one wondering just where one ends and the other begins. The result -- an incredibly readable novel in the tradition of Helen MacInnis and, yes, even Alistair MacLean.