It's a little tough as well, because any book on assembler, like the linked one is going to be generic ARM assembly. Since they only make the core and all the peripherals are specific to the manufacturers you're not going to get anything specific to the uC you are working with. I mean it's not going to be like a PIC or AVR guide with examples on how to setup I/O, UART, or anything like that.
ARM7 is not recommended for new designs by ARM, so don't get too attached to it.