I came across the following snippet when reading Endgame, a biography on Bobby Fischer (sorry, I cannot find a link here),
But Bobby was nothing but complex. Although much of his reading was confined to hate literature, he also embraced other works, such as Dag Hammarskjold's piquant book of aphorisms and poetry, Markings; and Eric Hoffer's The True Believer, which in many ways repudiates Armstrongism...
Most of the definitions I can find online is for 'nothing but + noun.' with the meaning of 'only, merely something'. But it doesn't really fit here in this context. Any ideas?