there really is none.
get a beginner piano teacher or something and you should pick up on it pretty fast

Elementary, my dear Watson! Actually, that is the best kind of books for mastering reading music. Elementary level instruction. Since you already play piano and sing, PRACTICE is the best remedy. Grab every piece of music you can find. First, make sure you know the spaces and the lines (F,A,C,E…Every,Good,Boy,Does,Fine) and your ledger lines. Every spare moment, name these notes from the music you find. Learn-if you don’t already know, scales, intervals, arpeggios. If you spend all your spare time re-enforcing what you already know–you can master it. The tough thing is just the repetition. When I majored in music, I HATED learning my scales, but after practicing like crazy, I learned them and found that concert playing (I played oboe) was a snap! everything is based on scales (even 12 tone–in it’s own way) and all scales are built on individual notes. I’m not sure what kind of “mastery” you are looking for, as a vocalist has different needs in reading music as compared to a pianist. No book will teach you mastery, only practice can do that. I hope that’s not a let down, but I’m not sure what you wish to master (sightreading by voice, two hand coordination on the keyboard, fluidity of naming notes…?) in any event, there is no quick fix except to know your basics and re-enfoce them EVERY chance you get. Below are some sources that might help.