The book is called, "A Door that Opens for All," and it's billed as halakha (Jewish law) for youth.
Look closely at the cover and what you'll see is a boy inside the ohel, mausoleum, knocking on the door of the Rebbe's old office in 770 Eastern Parkway, Brooklyn, NY.
And then look at the title again: "A Door that Opens for All."
Knock on the door, so to speak, and the Rebbe will answer your questions, requests and prayers.
Beseeching the dead or seeking to contact the dead is clearly forbidden in Jewish law. So is praying to the dead or requesting anything from the dead. That's why the Ben Ish Hai, the Sefardi rabbinic decisor of Jewish law from the late 1800s who often decides halakha based on the Zohar or on the Ari Zal, very clearly states that you cannot do these things when you visit graves of tzaddikim before the High Holidays. And that is the normative Ashkenazic halakha, as well.
But Chabad has never let halakha get in the way of their theology, which is becoming ever closer to Catholicism each day:
[Hat Tip: Yisrael Medad of My Right Word and the Menachem Begin Center.]