However, the Adventists had well-illustrated "Bible aids" long before JWs did.
Both groups are mired too much in the Old Testament. The Adventists have their adherence to various features of the Mosaic Law, and the JWs have "Jehovah." However, the Adventists are more mainstream in their beliefs about Jesus, according to some sources (i.e., like Walter Martin's The Kingdom of the Cults, page 517)
Both groups are also representatives of the Millennial Apocalyptic movement, and share a common "ancestor" in William Miller and his theology.
A good book for you, Eu, if you haven't read it already: Apocalypses, by Eugen Weber (Harvard University Press, 1999). It surveys the whole, failed, date-setting movement, from earliest times.