Encyclopedia Brown; Encyclopedia Brown's Book of Wacky Spies, by Donald J. Sobol. New York: William Morrow & Co. 128 pp. $9.50. (Ages 8-10.)

Any kid who likes spies will get a kick out of Encyclopedia Brown's latest compendium. Here we have World War I German spy Carl Hans Lody, ''the spy who lost the war.'' It was Lody who mistakenly reported that troops from Ross-shire on their way to France were ''troops from Russia.'' This caused the Germans to withhold two divisions from the Battle of the Marne to meet the Russian threat, thus losing that momentous battle.

Then there are the two German spies who landed in an encampment of Somerset Light Infantry and the two agents for George Washington who became partners in a coffeehouse in New York - neither knowing that the other was also an agent.

There's also the British spy who reported a hot tip concerning the planned kidnapping of a British commander in chief - five weeks after the plot failed.

There are successful spies, too, such as the Frenchman who could write a 1, 600-word report on a post card within the space allotted to a postage stamp, so that when the stamp was attached the report was completely covered.

As a whole, the book is fun and intriguing, although it reads more like ''Ripley's Believe It or Not'' than James Bond.