Would this considered to be cheating?

I was reading about openings and replaying Kasparov's win over Khalifman in 2002 when the latter used bird defense to Kasparov's Ruy Lopez opening. During my playback of that game, in one of my online games my oponnent started using the same defense. Right now the game just began and I'm playing exactly the same way Garry was playing in his win. Obviously it depends on my oponnent's moves, but I'm planning on following Garry's blueprint.

On one side I feel I should be using my brain to come up with my moves.

On the other side I feel that to become a better player I should use history to become more familiar with different defenses and attacks.

What is everyone's opinion on this?

I don't condone it very much but it's similar to the chess.com database that people use to play openings and such on turn-based. Not exactly skillful but that's allowed so I guess it shouldn't be considered cheating by using a similar method. Although maybe someone else could be more specific on the exact guidelines.

As far as I know the only way you can cheat is to use an engine or by consulting a person.

Book use is 100% legal in correspondence chess.

 Use You brain

The problem with this attitude is pretty clearly expressed in the OP's comments. If using a book during a game were frowned upon, what would this user be expected to do? Just simply stop reading the book just because he happens to be in a game with the same opening? That would make opening study difficult, as you would be unable to play correspondence because you might just run into another game using the opening you are reading about.

To the OP, be assured, you are not cheating, nor is what you are doing unethical. Play the game, read your book, learn from your game and from your book at the same time. But, if you go play a game in live chess, it's a good idea to close the book for the duration of your game there, just in case :-) .

You can cheat as you like, nobody will know anyway

In my previous tournament I stopped using my engine to study chess. After I finished my tournament I used the engine to analyze (some) of my games and of course doing some other researches. In my ongoing tournament, I'm running my engine to study 1.d4 openings (which I don't play in the tournament as I play 1.e4).

Let me check my engine status...

Ooops... It is running King's Gambit Cunningham Defense That's because somebody is posting about it on the forum But my KG games run in other variations. For example, the one with Black's Bishop going to the Queenside is something I totally don't understand. I'm planning to study this after the tournament.

This has got to be one of the best thread resurrections of the month; well played.