the best book vhdl
I have read all the books so far listed here.Amongst them I will rate Navabi Ashenden as for advanced level user as these unncessarily confuse a new user.
If you want a book that is comprehensive and self contained as well no talking around the bush.With simple examples. Then I would recommend.(SOme of the people who originally designed VHDL)
1. VHDL Made Easy David Pellerin; Douglas Taylor (BeST)
2. Jayaram Bhaskar Book (Second Good)
THe first one is also good if you are an intermediate user and want to just refer for quick refernce or syntax. The book has classified the Digital Logic design into its parts like sequential and combinational etc and how to do this in VHDL.
I think that is the right way to Design in VHDL.
IF you are advanced user you can also be fine by just reading VHDL LRM