Velikovsky was nuts. The planet Venus is just slightly smaller than the earth. Comets are vastly smaller bodies than an earth-sized planet...there is simply no way that a comet could have transmogrified itself into the planet Venus.
So tell me, have you read Worlds in Collision? Earth In Upheaval? or Ages in Chaos? Or don't you need to read a book to know a theory is wrong or the author is nuts?
http://www.thunderbolts.info/velikovsky-ghost.htm