David Bromberg made the leap from hotshot guitarist to solo artist in the ‘70s, mixing everything from Celtic reels and bluegrass tunes to blues-rock burners on his classic albums. Returning to recording in the '00s after an 18-year layoff, Bromberg issued two “theme” albums: an acoustic blues record and an all-star duets outing. As rewarding as those remain, Only Slightly Mad gives longtime Bromberg lovers the eclecticism of old once more. Things open with a sizzle on Bromberg’s incendiary, electrified (and electrifying) version of Blind Willie Johnson’s blues chestnut “Nobody’s Fault but Mine.” In due course, the singer/guitarist (with a crew including members of Levon Helm's band) slips seamlessly through everything from a singer/songwriter David Wiffen’s evanescent ‘70s folk-rock ballad “Driving Wheel” to The Stanley Brothers’ tragic bluegrass waltz “The Fields Have Turned Brown.” There's also a batch of Bromberg’s slyly syncretic original tunes. Of course, this eclecticism would be for naught if Bromberg didn’t color it all with the typically trenchant guitar work and charismatically quirky vocal delivery that earned him a diehard cult following to start with.