This book manages what others unfortunately fail to do: using a silly story concept seriously and making it work.
Of course, this story is not really complex. Big moral concepts won't be the main part of the hero's concerns. He is here to survive and protect the girl he has been sent here to protect. He will react to threats, take some preemptive actions, etc. Don't expect a depth of characters similar to Sanderson's work, for example.
But the way this modern engineer uses his mana magic is both funny and plausible. The way magic is an integral part of this world's society is a refreshing change to universes where mages are too rare or barely use their powers to do efficient work. And while the universe is not perfectly fleshed out (yet), and can be confusing at times (Greek gods have been what? by who? err, can you explain, please?), it is still defined enough to allow the story to go on.
As mentioned in other comments, the hero is powerful, but not omnipotent. He makes mistakes, he faces threats too big to defeat, in short, he is human. Oh, and he is definitely a male.
Indeed, the author is walking a fine line between unshameful sexual freedom and misogyny, but there are too many strong female protagonists (and heroins) for this series to be only the teenage fantasy of a male writer. Even though, in some parts... yeah, definitely, the author probably enjoyed his work a little too much and used it as a way to criticise ultrafeminists - but it's far from being in the same league as Gor, for example.
So, a pleasant reading, fast paced, witty and with not-too-perfect heroes that are quite likeable.