In 2000, her book on Irish History, The Researcher’s Handbook, was published by Limerick Corporation in 2000 and republished in 2002 in conjunction with the Irish Department of Education. This handbook was the first of its kind to deal with Irish source material.
In 2001, she co-authored Hard Lessons The Child Prisoners of Kilmainham Gaol. This was the first publication to examine the lives of child prisoners in Ireland. Aimed at the 9-12 age group, it has been used extensively by Irish primary schoolchildren and is in its third reprinting.
In 2003, No Ordinary Women: Activists in the Revolutionary Years 1900-1923 was co-published by the O’Brien Press & The University of Wisconsin Press. This again was an Irish best-seller, voted by Read Ireland as one of the top Irish history books for 2003. Also in 2003, Sinéad contributed to a number of books and a television documentary Guns and Chiffon for RTE. This television documentary was based on her books Guns and Chiffon and No Ordinary Women.