You have a great range of values here, and they all make sense the way you've applied them. I think the more applicable constructive criticism I could give would be regarding your shapes. Try to avoid tangents when you can -- they're areas where two objects, could be lines or shapes, come close to touching or just barely touch. They create tension and can distract the viewer if used unintentionally. Another very minor thing that you could do to reinforce the plane change is to bring that half tone up so it "curves" around the bottom of the pear on the right. These are both very small fixes. I think you have a great drawing here. Is there something specific with your values that you struggled with during this drawing?