Assalam u 'Alaikum.
In Surah Al-Fatihah,Guidance is of essence.We beg Allah for Guidance.And the Scholors often say that the greatest blessing Allah can bestow on his slaves in the Dunya,is bestowing them with guidance.The most important thing to notice is the fact that we ask for guidance.
Allah then starts Surah Al-Baqarah.

الم ذَلِكَ الْكِتَابُ لاَ رَيْبَ فِيهِ هُدًى لِّلْمُتَّقِينَ

"Alif, Lam, Meem.

This is the Book about which there is no doubt, a guidance for those conscious of Allah."

We ask Allah for Guidance in Fatihah and Allah replies that the guidance that we asked is,without a doubt this book.But not everyone can gain guidance.Note that Guidance is connected with inner peace,that ultimately,every human being is after.So the answer to achieving inner peace is said to be this book but only,the Muttaqeen can achieve guidance.The word مُتَّقِينَ,translated as "those conscious of Allah." comes from the root, و ق ى
which actually means "to protect, save, preserve, ward off."

Basically saying,only those who protect themselves and ward of evil can find guidance from this book in the truest meaning.For example,a Zani has to repent before Allah will make his heart TRULY receptive to this book.Repentance is the condition for truly gaining guidance from the Qur'an.It does not mean that the one committing major sins is a kafir,Allah forbid, nor does it mean that he or she should leave Salah and other good deeds untill they correct themselves.For Jihad against our own Nafs is one of the best deeds.What I wrote above is also supported by these following Ayahs.

"And We reveal of the Qur'an that which is a healing and a mercy for believers though it increase the evil-doers in naught save ruin." (17:82)

"Except for those who repent, believe and do righteous work...." (25:70)