The Gospel of Sri Ramakrishna’ was written and published by Mahendranath Gupta (14 July 1854 – 4 June 1932) in 1897 in English. Later in the form of Ramakrishna Kathamrita (শ্রীশ্রীরামকৃষ্ণ-কথামৃত) , a monthly series were published in several Bengali magazines (Tattva Manjari, Banga Darshan, Udbodhan). A single volume of Ramakrishna Kathamrita was published by Swami Trigunatitananda in 1902.
Present Kathamrita contain conversations of Ramakrishna (18 Feb 1836-16 Aug 1886) in five volumes (without maintaining chronology of incidents) from 19 February 1882 to 24 April 1886 and ‘recorded’ by Mahendra Nath Gupta. Mahendra Nath sourced it from his so called ‘diary'(nobody seen it). The volumes were published in Bengali in 1902 ,1902, 1904, 1908 , 1910 and 1932. Mahendra Nath hard the conversations of Ramakrishna and later he wrote it as his suitability as his own way. Swami Nikhilananda translated it in 1942. Later another translation by Dharam Pal Gupta was published. The stories were produced in the form of dialogue from his memories of actual conversations, as he claimed. The characters present in the conversations never mentioned anything as such in any other works, so there is no way to test the veracity of the truth.
It is said that Mahendra Nath was very close to Ramakrishna , but he never recorded anything about a period of three months(May-August of 1886) before the death of Ramakrishna.