Recommend takes an object. Whatever the object is is what is being recommended.
There's a difference between the literal meaning of these two sentences:
- We'd recommend you to book your flight early.
- We'd recommend to you to book your flight early.
In sentence #1, the thing being recommended is 'you'. This means that, out of all the people who could potentially book the listener's flight early, the speaker thinks that the best person to do so would be the listener. In other words. This sentence takes booking the flight early as a given, and simply considers who should do it.
In sentence #2, the speaker is recommending "to book your flight early". This is a course of action. They think the listener should book their flight early.
Obviously, the literal meaning of sentence #1 would not make much sense in most situations. This, combined with context, would likely lead me to believe that they intended the meaning of sentence #2. In other words, the first is not particularly well constructed, but would probably be understood to mean the second.
I've looked in several dictionaries for the usage of recommend found in #1. The only one I found that attributed the meaning of sentence #2 to sentence #1 noted that it is considered wrong by some, and recommended to instead use the form in sentence #4, found below.
Some more common ways to phrase this thought include:
- We'd recommend you book your flight early.
- We'd recommend that you book your flight early.
"You book your flight early" is an action that is being recommended, but it sounds like an odd phrasing by itself. Instead, I would use a different tense:
- We'd recommend booking your flight early.