The old reliable source is still E. Merton Coulter's "Civil War and Readjustment in Kentucky." William Davis's "Breckinridge: Statesman, Soldier, Symbol" gives a thorough treatment of the Kentucky neutrality issue. Volume I of Collins's "History of Kentucky" will give you a sequence of events but not much of the rationale behind them. Also try Peter Sehlinger's "Kentucky's Last Cavalier: Gen. William Preston" as well as Z.F. Smith's "History of Kentucky" and Thomas Speed's "The Union Cause in Kentucky."
You'll find through all of these that the House and Senate only passed resolutions of neutrality, which had no legal status and weren't worth the paper they were printed on.
Hope this gets you started in the right direction.