From Dale Thorn's review of Mark Lane's excellent book "The Last Word"

BOOK THREE - The Secret Service (Chapters 14 to 19):

I thought by now I had read everything on the JFK assassination, especially about the rather obvious and visible Secret Service. Be prepared for some surprises. Where the Warren Commission glossed over the Secret Service "failures" the day of the assassination, the HSCA set the record straighter: "No actions were taken by the agent in the right front seat of the Presidential limousine to cover the President..." In fact, the two agents in the President's car and the eight agents in the car immediately behind the President did nothing between the first shot and the final shot more than six seconds later. By contrast, the agents in the Vice-President's car acted immediately on the first shot to protect the Vice-President, jumping on him and covering him completely.

A fascinating tidbit I had been unaware of is that 11 of the most experienced members of the White House Secret Service detail were transferred to other assignments in the 60 days preceding the assassination. There is no explanation for that as far as I know.

One former Secret Service member, Gerald Blaine wrote the book The Kennedy Detail in 2009, endorsing the Warren Report and offering explanations for the behaviors of the various agents the day of the assassination, although Blaine was not in Dallas that day. Errors and omissions abound in Blaine's book, among which are not knowing the nature of Drew Pearson's employment or reputation when they dismissed his newspaper column criticizing the Secret Service on December 1, 1963. Worse is Blaine's assertion that Pearson got it all wrong in his column about the agents' behavior the night before the assassination, when Pearson stated that the agents were out drinking until the wee hours of the morning.

Blaine's accusations against former agent Abraham Bolden are also telling, where Blaine states that there was no corroboration of any of Bolden's stories about the Secret Service and the virulent racism he encountered there. According to Mark Lane, Blaine states several times in his book that there was never a hint of racism in the Secret Service, although nearly 10 years before Blaine's book the Washington Post reported that a number of African-American Secret Service agents had applied to the Equal Employment Opportunity Commission to file a class action lawsuit against the Secret Service for racial discrimination. In 2007, National Public Radio reported that "58 African-American Secret Service agents issued sworn statements in a class action lawsuit claiming racial discrimination by the agency."