Surplus People: From Wicklow to Canada, a book written by Jim Rees, was first published under the title Surplus People: The Fitzwilliam Clearances 1847-1856. The book is being released under the new title later this month by Collins Press of Cork. The population of County Wicklow decreased by over 20% during the Great Famine. Of the 27,000 people who left, about 6000 were residents of the Wicklow Coolattin Estate owned by Lord Fitzwilliam. Here's the description of the new book on Amazon.com:

The Great Famine in Ireland was a catastrophe of immense proportions. Eviction, emigration and death from starvation were widespread. Landlords, eager to dispose of 'surplus' tenants, engaged in 'assisted passages', whereby tenants were given financial incentives to emigrate. The clearances of uneconomic tenants from the 85,000-acre Coolattin Estate in County Wicklow by Lord Fitzwilliam were the most organised in Ireland during and after the Famine years. From 1847 to 1856 Fitzwilliam removed 6,000 men, women and children and arranged passage from New Ross in Wexford to Canada on emigrant ships such as the Dunbrody. Most were destitute and many were ill on arrival in Quebec and New Brunswick. Hunger and overcrowding at quarantine stations, such as the infamous Grosse Ile, resulted in further disease and death. Jim Rees explores this tragedy, from why the clearances occurred to who went where and how some families fared in Canada.

A book review in the April 2014 edition of Ireland's Genealogical Gazette paints a vivid picture of conditions at the Grosse Ile quarantine station:

...On May 14th 1847 the first ship arrived at Grosse Ile and within two weeks there were a further 30 ships at anchor with some 10,000 passengers awaiting medical inspection. On June 3rd the healthy were moved to the east of this island with an armed guard dividing the healthy from the sick. By June 9th a further 36 ships had arrived from other parts of Ireland with a further 13,000 passengers on board. The daily death rate rose at this stage to some 50 a day...

Either of Jim Rees' Surplus People editions would be illuminating, particularly if your ancestors passed through Grosse Ile during this time period.