Cover art
Laumer, Keith. Worlds of the Imperium. Tor 1982.

Laumer, Keith. Crosstime Imperium
Series note: Four volume series, containing Worlds of the Imperium, The Other Side of Time, Assignment in Nowhere, and Zone Yellow. The middle two volumes were collected in the omnibus volume Beyond the Imperium. The first three volumes were collected in the omnibus volume Imperium.

Cover art
Laumer, Keith. Worlds of the Imperium. Positronic 2023.

Laumer, Keith. Worlds of the Imperium
Divergences: 1790 CE, 1911 CE
Summary: A man from our world becomes an agent for a world run by an Anglo-German imperium, and visits another where civilization fell after Germany won World War I.
Series note: First of the Crosstime Imperium tales.
Published: Ace Double #F-127 (Ace 1962); Berkley 1977; Tor 1982 (0523485468); exp. Tor 1983 (0523485425), 1986 (0812543793BUY, 0812543807); Dover 2017 (0486808661BUY); Positronic 2023 (1515445054BUY)
— Originally serialized in Fantastic Stories, February through April 1961
— Included in Imperium
— Included in Three by Laumer, Gollancz 2017 (1473215994BUY).
Original in: English.
Translation: French by Bruno Martin as Les Mondes de l'Imperium, Opta 1971.
Translation: Italian by Lucia Morelli as I Mondi dell'Impero, La Tribuna 1964.
Translation: Portuguese by Eurico Fonseca as Mundo Alternante, Livros do Brasil 1969.
Translation: Russian as Miry imperiuma, Tsentrpoligraf 1992.
Translation: Spanish by Horacio González Trejo as Mundos de imperio, Martínez Roca 1978 (8427004253).
Translation: Swedish by Torkel Franzen as Imperiets världar, Laisses faire 1983 (9176480089).

Cover art
Laumer, Keith. The Other Side of Time. Berkley/Medallion 1965.

Laumer, Keith. The Other Side of Time
Divergence: 1814 CE
Summary: Our hero is trapped in a timeline where Napoleon won a glorious victory at Brussels in 1814.
Series note: Second of the Crosstime Imperium tales.
Published: Berkley/Medallion 1965; Walker 1971; Signet 1972 (0451052552BUY).
— Originally serialized in Fantastic Stories, April through June 1965.
— Included in Beyond the Imperium and Imperium.
Original in: English.
Translation: German by Peter Kleinert as Invasion aus der Null-Zeit, Bastei 1973 (3404000587).
Translation: Spanish as Al otro lado del tiempo, publ. unknown.

Laumer, Keith. Assignment in Nowhere
Divergence: 1199 CE
Summary: The last Plantagenet visits a timeline where Richard Couer de Lion avoided battle at Chaluz but succumbed to French conquest in his old age.
Series note: Third of the Crosstime Imperium tales.
Published: Berkley 1968; Dobson 1972 (0234776323).
— Included in Beyond the Imperium and Imperium.

Laumer, Keith. Zone Yellow
Summary: Concluding with conflict versus a crosstime invasion of rat-like creatures.
Series note: Fourth of the Crosstime Imperium tales.
Published: Baen 1990 (0671720287).

Cover art
Laumer, Keith. Beyond the Imperium. Tor 1986.

Laumer, Keith. Beyond the Imperium
Comments: Omnibus of The Other Side of Time and Assignment in Nowhere.
Published: Tor 1981 (0523485131), 1986 (0812543815, 0812543823).
Original in: English.
Translation: Nederlands by Mike Grothaus as De Komst van de Chaos + Invasie uit de Dimensies, Meulenhoff 1974, 1980 (9029002581).

Laumer, Keith. Imperium
Comments: Omnibus of Worlds of the Imperium, The Other Side of Time and Assignment in Nowhere.
Published: Baen 2005 (0743499034BUY).