Short Answer

No it did not, previous Anglo-Saxon law codes were similarly universal. Other cultures, particularly the Visigoths, also held rather strongly that king and peasant had to abide by the same laws.

Long Answer

I first want to clear up a little misconception in the question. Although Anglo-Saxon law applied to almost everyone, there were two groups which were outside of the law: foreigners, and the king himself. Early Anglo-Saxon law worked by forcing everyone to swear an oath to the king to follow the laws, giving the king the right to give punishments for breaking that oath in accordance to what the breach was. This meant that new immigrants and foreign merchants were essentially outside of the law since they had not taken the oath. It also meant that the king was above the law since they couldn’t take an oath to themselves and was the ultimate arbiter of what the law was. In practise though, kings generally followed most of their own laws.

The almost universal nature of Alfred’s law code was not new, it expanded a long-standing Anglo-Saxon legal tradition. The Dooms go back to at least the 6th century; the earliest one we have comes from Æthelberht, King of Kent from 560-616 AD.

Central to Anglo-Saxon law was the bot. The bot roughly translates to financial compensation for physical harm, preferably to be paid in hard currency but in goods of equivalent value if the criminal did not have enough. It emerged as a way to break the cycle of violence created by blood feuds; such feuds could simply be paid away and everyone could go back to farming rather than stabbing their neighbours. Æthelberht’s code sets out compensation for a great many injuries, mandating things like ‘If any one strike another with his fist on the nose, three shillings.’ and ‘if he pierce [the genitals], let him make bot with six shillings’. Yes, a nail through the penis carried only twice the compensation of being punched in the nose (as long as the genitals still worked; rendering someone infertile carried a different penalty - they really thought of everything). The bot was a fixed penalty and could not be deviated from, though by the 10th century, age, illness and infirmity were taken into account when giving out penalties and a basic appeals process was in place.

Closely related to the bot were the leogeld and wergeld. These were the value of someone’s life depending on their social standing, to be paid to the victim’s family in the event of their death. Leogeld covered accidental death, wergeld covered homicide. This also seems to have covered battles, and even kings were expected to pay it - the 9th century monk Bede relates how King Ecgfrith received compensation after his brother was killed in a battle.

The bot was universal, but the leogeld and wergeld were not. It was not universally applied in Æthelberht’s code, as it states ‘If the king's ambihtsmith, or laadrinc, slay a man, let him pay a half leodgeld.’ To translate, this clause meant that if someone doing a job for the king accidentally killed someone, then they only had to pay half the usual penalty. We do not know to what extent laws carried over to the next king, so we do not know how long this exception remained in practise. It may very well have still been in use when Alfred was king.

You can read all of the Dooms here: https://sourcebooks.fordham.edu/source/560-975dooms.asp#The%20Laws%20of%20King%20Alfred

As to whether this was something unique to Anglo-Saxon law, it was not. The Visigothic law code, written in the mid 7th century, survives almost in full and contains the following clause about it’s judges, emphasis mine:

“The Judge should be quick of perception; firm of purpose, clear in judgment, lenient in the infliction of penalties; assiduous in the practice of mercy; expeditious in the vindication of the innocent: clement in his treatment of criminals; careful of the rights of the stranger; gentle toward his countrymen. He should be no respecter of persons, and should avoid all appearance of partiality.”

It was expected that even if the case was a peasant against a nobleman, the judge should treat them both the same. It also says that “The law rules every order of the state, and every condition of man; it governs wives and husbands; youth and age: the learned and the ignorant, the polished and the rude. It aims to provide the highest degree of safety for both prince and people.” This clause states that the law is there for everyone, not one for the rich and another for the poor. An exception was the treatment of slaves, if a slave was harmed only half the normal penalty was to be paid, though everyone was still expected to pay said penalty.

Visigothic law actually goes a lot further than Anglo-Saxon law in asserting its universality, and in restraining royal power, in a way that would not be really seen again until Magna Carta. It stated: “no person of whatever rank or dignity may refuse to submit to the power of the law” in a section titled "The Royal Power, as well as the Entire Body of the People, should be Subject to the Majesty of the Law." There is another section called "How the Avarice of the King should be Restrained in the Beginning, and How Documents Issued in the Name of the King should be Drawn Up". They held that the law came from God, and as such king and peasant had to follow it alike.

The full Visigothic code can be found here: http://www.documentacatholicaomnia.eu/03d/0506-0506,_AA_VV,Leges_Romanae_Visigotorum[Scott_JP_Curatore],_EN.pdf

Other Germanic law codes also contained similar concepts to the wergeld and the bot. The Lex Ripuaria, a Frankish law code written around 630 AD, contains very similar lists of compensation for wounds and death. It even uses the word wergeld. It seems that the bot, and its universality, was a staple of Germanic justice before they established kingdoms in France and Britain. This was gradually broken down in the Carolingian Empire as nobles got concessions from the Holy Roman Emperor which gave them privaleges over the law, whilst in Britain the Normans supplanted Anglo-Saxon laws with their own which favoured Norman landowners over the locals. As for the Visigoths, their legal code faded into obscurity after the Arab Conquest destroyed the Visigothic kingdom. A shame really; their legal system was centuries ahead of its time.

Secondary sources:

Lambert, T. B. "Theft, Homicide and Crime in Late Anglo-Saxon Law." Past & Present 214.1 (2012): 3-43.

Rubin, Stanley. "The Bot , or Composition in Anglo‐Saxon Law: A Reassessment." The Journal of Legal History 17.2 (1996): 144-54.

Roach, Levi. "Law Codes and Legal Norms in Later Anglo‐Saxon England." Historical Research 86.233 (2013): 465-86.

I totally had this confused with something else, was there a similarly named book in English history for the first country-wide census ever conducted, and that it got its name because it was so detailed it would last until doomsday? I believe its detail was mostly for taxation purposes

I studied this while earning my undergraduate degree in criminology.

The “Dooms of Alfred” were one of the larger legal referendums at the time. Previous Kings had made changes to the law but it wasn’t until king AEthelberht around 597 AD that they were translated and documented into English law. So previous laws may or may not have influenced king Alfred.

The Dooms has such a great impact because it categorically indexed crimes and their punishments mostly payments of shillings for damages, instead of imprisonments which still left the victim behind.