From Wikipedia:
"Deinonychus antirrhopus is one of the best-known dromaeosaurid species, and is a close relative of the smaller Velociraptor, which is found in younger, Late Cretaceous–age rock formations in Central Asia. The clade they form is called Velociraptorinae. The subfamily name Velociraptorinae was first coined by Rinchen Barsbold in 1983 and originally contained the single genus Velociraptor."
Basically this means that at the time Crichton wrote the first book, Deinonychus antirrhopus was in fact a species within the single genus Velociraptor, hence the naming.
Later it was finally put it in it's own genus Deinonychus.