I was looking for this book, Look To the Rock by Alec Motyer. If you would look for it in Amazon, you would see that its price ranges from 50 USD and up.
This is one of the books most recommended by Tim Keller that helped his preaching and is continually helping him preach Christ-centeredly.
If you are interested, I ask the seller to send you only for 25 USD, inclusive of shipping. Or drop me a note. I think there are still 3 copies available.