As the first in a triple stack of fifteens, LEADEROFTHEPACK is a nice start, and apt. Apt! The next two in the top triple became clear as I chipped away at the downs. I had heard of an ALFAROMEOSPIDER but I was not familiar with Notorious B.I.G.'s oeuvre GOINGBACKTOCALI.
The bottom triple stack was more of a challenge. Thanks to a few key downs, including the familiar old chestnut Bert CONVY, I was able to guess the middle fifteen, ALLOVERCREATION. But, while I have heard of MATRYOSHKADOLLS, if someone had asked me if I could spell the name of them off the top of my head, I would have said NOMAAM. ALAINRENELESAGE rang a vague bell, once I completed the answer thanks to copious guessing on the downs, but the name didn't leap to mind. I read a bit about the man on the Wikipedia. He seems like an interesting guy. Maybe I'll read "Gil Blas."
Flanking the fifteens were a COPA other good entries. To wit:
New toy? (PUP) - cute
Pair of nines? (ENS) - fooled again!
Tar (OLDSALT) - both such flavorful nouns
Prepare for a bomb, say (GODEEP) - nicely ambiguity
Brother-to-be (PLEDGE) - I was sidetracked by the religious kind of brother
Place to count sheep (LEA) - It took me too long to put this one to bed
Interesting to learn that AIRMAIL commenced in 1911. So near, and yet so far.