I got the impression the reason Hank didn't say anything yet is because of how his superiors handled his other leads. He suspects Jesse, they make him lay off Jesse. He suspects Mike, 'The budget for surveilling Mike is now zero dollars'. If he's going to toss up his own brother in law as a suspect, he better have conclusive proof, that wasn't acquired by removing an object from the suspect's home without a warrant.
The more I think about it, the dumber it was to take the book with him when he left. He has basically made his only evidence against Walt inadmissable (Legal experts correct me if I'm off base). Now what else does he have? He has the fact that the original lab equipment found in the RV came from Walt's classroom. I suppose he could destroy the 'gambling winnings' story for Walt's sudden infusion of cash pretty easily. All the other physical evidence is destroyed. I don't see what he could do to Walt without flipping someone. And TBH, I think the most likely person to flip is Skylar, not Jesse.
It shouldn't be too hard for Hank to figure out Skylar is an accomplice. Soon he's going to think about the timing of the divorce and the fact that she came up with the idea to pay for his rehab, she came up with the gambling story, and she runs the car wash.