most are packed away right now, so by memory....
A Retrospective, by McGregor (http://www.goodreads.com/book/show/2126976,)Bob_Dylan_A_Retrospective, collection of different printed articles on Bob in the 60's. Couple that with Scaduto' 'Bob Dylan: Biography' (up to JWH at least)...http://www.goodreads.com/book/show/132054.Bob_Dylan and you get a nice '60's summary.
Each one of Michael Gray's 'Song and Dance Man' from the mesmerizing first one through to the epic third.
(Song & Dance Man: The Art Of Bob Dylan (1972, 1973); The Art Of Bob Dylan: Song & Dance Man (1981, 1982);
Song & Dance Man III: The Art of Bob Dylan. Continuum. 1999, 2000. ISBN 0-8264-5150-0)
Always fun to pick up Paul William's 'Performing Artist' series and listen to the concerts he writes about.
Best Heylin, for me, was a little small collection of Bob's preacher rants in the born again days (http://www.taxhelp.com/heylin-saved.html) and for actual writing you can't beat his contributions in the Telegraph fanzine edited by the late and much lamented John Bauldie, and collected partly in 'Wanted Man'
http://www.goodreads.com/book/show/417926.Wanted_Man and in 'All Along the Telegraph' co-edited by Bauldie and Gray, which is just as great,
http://eil.com/products/Bob+Dylan/All+Across+the+Telegraph+-+A+Bob+Dylan+Handbook/Bob+Dylan+All+Across+the+Telegraph+-+A+Bob+Dylan+Handbook%20550643.html. On his own, Heylin seems to 'reach' too far for my liking...better in small doses.
Not much to say about Marcus, and I wish I could have got into Rick's, but so much pretension sinks them both, methinks.