"This book i[the Bible] is the Holy Book of God, of celestial Inspiration. It is the Bible of Salvation, the Noble Gospel. It is the mystery of the Kingdom and its light. It is the Divine Bounty, the sign of the guidance of God."
Answers to many questions asked by Christians are in Some Answered Questions, by 'Abdu'l-Baha, which you can read here.
What do Baha'is believe about Jesus and Christianity?
“As to the position of Christianity, let it be stated without any hesitation or equivocation that its divine origin is unconditionally acknowledged, that the Sonship and Divinity of Jesus Christ are fearlessly asserted, that the divine inspiration of the Gospel is fully recognized...
Know thou," Bahá'u'lláh has moreover testified, "that when the Son of Man yielded up His breath to God, the whole creation wept with a great weeping. By sacrificing Himself, however, a fresh capacity was infused into all created things. Its evidences, as witnessed in all the peoples of the earth, are now manifest before thee. The deepest wisdom which the sages have uttered, the profoundest learning which any mind hath unfolded, the arts which the ablest hands have produced, the influence exerted by the most potent of rulers, are but manifestations of the quickening power released by His transcendent, His all-pervasive and resplendent Spirit. We testify that when He came into the world, He shed the splendor of His glory upon all created things.... He it is Who purified the world. Blessed is the man who, with a face beaming with light, hath turned towards Him."
Shoghi Effendi, The Promised Day is Come, p. 109-110
"... the foundations of Christianity and the religion of Bahá'u'lláh are one. ... Whoever acts completely in accordance with the teachings of Christ is a Baha'i. ... The purpose is the essential meaning of Christian, not the mere word. The purpose is the sun itself and not the dawning points. For though the sun is one sun, its dawning points are many. We must not adore the dawning points but worship the sun. We must adore the reality of religion and not blindly cling to the appellation Christianity. The Sun of Reality must be worshiped and followed. We must seek the fragrance of the rose from whatever bush it is blooming -- whether oriental or western. Be seekers of light, no matter from which lantern it shines forth." 'Abdu'l-Baha