The private notebook of Bram Stoker has been discovered in an attic on the Isle of Wight, offering cryptic clues into the origins of the author's most famous work, Dracula.

Providing a snapshot of Dublin between 1871 and 1881, as well as a window on the life of the very private Stoker, the notebook was found by the author's great-grandson, Noel Dobbs. Dobbs sent photographs of pages from the book to his relative, Stoker's great-grandnephew Dacre Stoker, author of the recent novel Dracula: The Un-Dead, and Stoker has worked to decipher his ancestor's "terrible" handwriting with Dr Elizabeth Miller of the Transylvanian Society of Dracula. The Lost Journal, complete with annotations, is now lined up for publication by Robson Press next year, marking the centenary of Bram Stoker's death in 1912.

The 100-odd-page notebook covers the period when Stoker was a student at Trinity College in Dublin and a clerk at Dublin Castle, written in a clear precursor to the journalistic style of Dracula and containing the author's earliest attempts at poetry and prose. "There are some definite parallels between this notebook and Jonathan Harker's journal, and certain entries from Bram's notebook actually resurfaced twentysomething years later in Dracula. Because he wrote little about himself, Dracula fans and Stoker scholars have largely been free to speculate about Bram. Rumours and myths have taken on a life of their own. Now, with this chapter of Bram's life revealed, the rest of his life will be more accurately interpreted," said Dacre Stoker.

The notebook opens with an entry entitled Night Fishing – the earliest known example of Stoker's writing – which Dacre Stoker and Miller said "shows an aspiring writer composing an excessively descriptive passage in flowery prose". It also reveals the author's connection with the sea and his respect for the people at its mercy, an interest which would re-emerge in published works including Dracula (1897), The Watter's Mou' (1894), The Mystery of the Sea (1902) and Greater Love (1914).

Another entry reads "A man builds up a shadow on a wall bit by bit by adding to substance. Suddenly the shadow becomes alive", and would later become the kernel for Stoker's story The Shadow Builder. A note reading "'Palace of Fairy Queen. Child goes to sleep & palace grows – sky changes into blue silk curtains" foreshadows Stoker's frequent use of dreaming children in stories including Lies and Lilies and The Wondrous Child.

Although the notebook ends eight years before Stoker would begin writing Dracula, there are "several entries" in the book which have "distinct resonances" in the novel, said Dacre Stoker and Miller, including a man who "who reflects everybody's self who meets him" – a central motif of Dracula is that a vampire casts no reflection.

Another mentions "a little boy who put so many flies into a bottle that they had not room to die". "This image is very interesting to me as it is a precursor to the tendencies of Bram's Renfield character in Dracula," said Dacre Stoker.