Indiana Jones and the Secret of the Sphinx

I have just finish Secret of the Sphinx. I would say with confidence, it is the most bizzare of the entire Bantam Indiana Jones series. Good sidequest opening searching for Qin's tomb in the mountains of China (already trying to Legoize some of those traps-I'm thinking ancient Chinese flamthrower) then kind of sinks in to a '30 Asia-is-a-bad-place-to-be description of Indy's escape from a Japanese prison, including a torture-helmet (worse than waterboarding) and this misrable Bryce guy. Then it slowly picks up with a hunt for not one, but two mystical artifacts-the Staff of Aaron and the wholy ficticious Omega Book. It does not feel like Indiana Jones-like a bridge between novels, with a strange misplacement of elements that make up a great Indy story.
Also, there is a kind of afterword involving the Crystal Skull of Cozan-first mention in the beginning sidequest of Philosopher's Stone and at the end Indy says, "...I have had some unusal experences, in which miracles seemed posible. Time travel, even." I immediatly thought of the Indy novel LucasBooks turned down by one of Bantam's writers because it was too science-fiction and had elements of time travel. After all, when Indy said it, he was talking to what the book describes as "the world's foremost authority on time" a "professor". Einstein? I'm going to reseached that a little.