Fluffy

Suetonius used the imperial archives to research eyewitness accounts, information, and other evidence to produce the book.
However, critics say the book is founded on gossip and citations of historians who had lived in the time of the early emperors, rather than on primary sources of that time. The book can be described as very racy, packed with gossip, dramatic and sometimes amusing. There are times the author subjectively expresses his opinion and knowledge.
Though he was never a senator, Suetonius took the side of the Senate in most conflicts with the princeps, as well as the senators' views of the emperor. This resulted in biases, both conscious and unconscious. Suetonius lost access to the official archives shortly after beginning his work. He was forced to rely on second-hand accounts when it came to Claudius (with the exception of Augustus' letters which had been gathered earlier) and does not quote the emperor.
Despite this, it provides valuable information on the heritage, personal habits, physical appearance, lives and political careers of the first Roman Emperors. It mentions details that other sources do not. For example, Suetonius is the main source on the life of Caligula, his uncle Claudius, and the heritage of Vespasian (the relevant sections of the Annals by his contemporary Tacitus being lost). Suetonius made a reference in this work to "Chrestus", which may refer to "Christ". During the book on Nero, Suetonius mentions a sect known as the Christians (see Historicity of Jesus). Like many of his contemporaries, Suetonius took omens seriously and carefully includes reports of omens portending Imperial births, accessions and deaths.

Life of Julius Caesar

The first few chapters of this section are missing. Suetonius begins this section by describing Caesar's conquests, especially in Gaul and his Civil War against Pompey the Great. Several times Suetonius quotes Caesar. Suetonius includes Caesar's famous decree, "Veni, vidi, vici" (I came, I saw, I conquered). In discussing Caesar's war against Pompey the Great, Suetonius quotes Caesar during a battle that Caesar nearly lost, "That man (Pompey) does not know how to win a war."
Suetonius describes an incident that would become one of the most memorable of the entire book. Caesar was captured by pirates in the Mediterranean Sea. Caesar engaged in debate and in philosophical discussion with the pirates while in captivity. He also promised that one day he would find them and crucify them (this was the standard punishment for piracy during this time). When told by the pirates that he would be held for a ransom of 20 talents of gold, Caesar laughed, and said that he must be worth at least 50 talents. Just as he had promised, after being released, Caesar captured the pirates and crucified them.
It is from Suetonius that we first learn of another incident during the life of Julius Caesar. While serving as governor in Hispania, Caesar once visited a statue of Alexander the Great. Upon viewing this statue, Suetonius reports that Caesar fell to his knees, weeping. When asked what was wrong, Caesar sighed, and said that by the time Alexander was his (Caesar's) age, Alexander had conquered the whole world.
Suetonius describes Caesar's gift at winning the loyalty and admiration of his soldiers. Suetonius mentions Caesar commonly referring to them as "comrades" instead of "soldiers." When one of Caesar's legions took heavy losses in a battle, Caesar vowed not to trim his beard or hair until he had avenged the deaths of his soldiers. Suetonius describes an incident during a naval battle. One of Caesar's soldiers had his hand cut off. Despite the injury, this soldier still managed to board an enemy ship and subdue its crew. Suetonius mentions Caesar's famous crossing of the Rubicon River, (the border between Italy and Cisalpine Gaul), on his way to Rome to start a Civil War against Pompey and ultimately seize power.

Life of Claudius

Claudius was the brother of Germanicus, the father of Caligula. He was descended from both the Julian and the Claudian clans, as was Caligula. He was about 50 years old at the time of Caligula's murder. He never held public office until late in his life, probably due to his family's concerns as to his health and mental abilities. Suetonius has much to say about Claudius' apparent disabilities, and how the imperial family viewed them, in the Life of Augustus.
The assassination of Caligula caused great terror in the Palace and, according to Suetonius, Claudius, being frightened by the sounds of soldiers scouring the Palace for further victims, hid behind some curtains, being convinced that he would be murdered as well. A soldier checking the room noticed feet sticking out from underneath the curtains, and upon pulling back the curtains discovered a terrified Claudius. Upon the arrival of other soldiers to the room, they acclaimed Claudius emperor and hustled him out of the Palace. Claudius was taken to the Praetorian camp, where he was quickly proclaimed emperor by the troops.
We learn from Suetonius that Claudius was the first Roman commander to invade Britain since Julius Caesar a century earlier. Cassius Dio gives a more detailed account of this. He also went farther than Caesar, and made Britain subject to Roman rule. Caesar had "conquered" Britain, but left the Britons alone to rule themselves. Claudius was not as kind. The invasion of Britain was the major military campaign under his reign.
Suetonius says Claudius suffered from ill health all of his life until he became emperor, when his health suddenly became excellent. Claudius suffered from a variety of maladies, including fits and seizures, as well as several disagreebale personal habits like a bad stutter and excessive drooling. Suetonius accuses Claudius of cruelty and stupidity, assigning some of the blame to his wives and freedman.
Suetonius discusses several omens that foretold the assassination of Claudius. He mentions a comet that several Romans had seen shortly before the assassination. As mentioned earlier, comets were believed to foretell the deaths of significant people. Per Suetonius, Claudius, under suggestions from his wife Messalina, tried to shift this deadly fate from himself to others by various fictions, resulting in the execution of several Roman citizens, including some Senators and aristocrats.
Suetonius paints Claudius as a ridiculous figure, belittling many of his acts and attributing his good works to the influence of others. Thus the portrait of Claudius as the weak fool, controlled by those he supposedly ruled, was preserved for the ages. Claudius’ dining habits figure in the biography, notably his immoderate love of food and drink, and his affection for the city taverns.
His personal and moral failings aside however, most modern historians agree that Claudius generally ruled well. They cite his military success in Britannia as well as his extensive public works. His reign came to an end when he was murdered by eating from a dish of poisoned mushrooms, probably supplied by his last wife Agrippina in an attempt to have her own son from a previous marriage, the future emperor Nero, ascend the throne.