A CIA agent parked in front of the police station, went in, flashed his creds, explained his mission to the extent he could, meaning it was mostly refined by-the-spook-book gobbledygook, and got zip for his troubles from the lawmen who were understandably excited that a dangerous desperado might be in their midst, but not very helpful.

What does "by-the-spook-book" mean?
A 'spook' is a spy.
'By the book' means 'according to regulations'.

However, the passage is so riddled with slang that I would not even attempt to interpret the whole of it.
NewguestWhat does "by-the-spook-book" mean?
Doing something by the book means that you do something in accordance with the written regulations of your profession.

"Spook" is an American word for spy or secret agent.
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