Was it a BJP landslide?

Yes and no. Yes in terms of total seats won (282 of 545; more than that if you count the BJP's alliance partners); no in terms of total vote percentage, which was 31% (at least that's the figure I heard on the NewsHour). The disjunction is explained by the single-member-district system and the fact that relatively few of the BJP's votes were wasted -- i.e., in districts where it lost, it often lost by large margins whereas in districts where it won, it often won by smallish margins. Or so one gathers from an analysis at the Monkey Cage, quoted at the end of this post by P.A. Foster, who includes links to the coverage in various places.

ETA: The map reproduced at the linked post shows the Congress Party, trounced on the whole, did very well in a few places, including the extreme east, which showing may have been a result of fairly harsh recent govt crackdowns -- if I'm not mistaken -- on the long-running armed insurgencies there. Btw, Harvard history professor Sugata Bose ran for a seat as a Congress candidate in W. Bengal; I don't know whether he won and am not taking the time to look it up right now.