jewish books - Igrot Kodesh of the Lubavitcher Rebbe zt'l

There is a practice among Chabad chasidim to ask questions via the "Igrot Kodesh" (a collection of published correspondence from the seventh Lubavitcher Rebbe).

The procedure involves writing a letter and placing it in a random volume and page of Igrot Kodesh, and then reading the response.

Is there any problem with doing this? Halachically or otherwise. Please source.

I had asked a Chabad person once whether this is praying to the Rebbe (which would certainly be forbidden) and he replied something like that it is "asking for a beracha".