user_book_interaction = pd.pivot_table(interactions_selected, index='user_id', columns='book_id', values='rating')
# fill missing values with 0
user_book_interaction = user_book_interaction.fillna(0)
user_id = list(user_book_interaction.index)
user_dict = {}
counter = 0 
for i in user_id:
    user_dict[i] = counter
    counter += 1
# convert to csr matrix
user_book_interaction_csr = csr_matrix(user_book_interaction.values)
user_book_interaction_csr