Beatles Recording Techniques?

The wikipedia articles are very good and include information from the 'Complete Beatles ..' book.
It seems to me that it's impossible to give a summary of Beatles recording techniques because they used so many. They really were pioneers at the time and tried almost everything that they could to get new sounds. They were not 'technical' people. Here are some basic facts that might help.
They mostly used four-track tape machines, sometimes with two linked together. Because of the limited number of tracks they were very economical with space and in the early recordings would record 'live' takes of four or three of them playing and/or singing at once.
They were more concerned with the mono mix than the stereo which was usually worked on later. Try playing just one channel from the early recordings and you can hear just the vocals or the rhythm section sometimes.
Vocals were often double-tracked simply by singing the vocal twice. Later they used automatic double tracking ADT on some recordings, they would double track guitar parts too.
They would sometimes speed up or slow down tapes to create effects. Strawberry Fields is an extreme example of this.
The drums were often muffled to give a thicker sound, e.g. coats were put in the bass drum, cloths put over the snare, etc.
They used acoustic pianos a lot and would often have two or more pianos playing on one song.
Guitar solos were usually done without much reverb.
Getting new sounds was very important to them and they would spend a huge amount of time experimenting with this.
Importantly they had George Martin and a team of engineers to work to get the sounds they wanted!

Have to agree completely with Kim. Benny Gallagher who worked with the Beatles said that the thing that held the recordings together was the bass and that George Martin would use it as the centre for each recording , though he was referring more to McCartney's playing than the actual instrument itself. I've tried a replica and I found it really unpleasant to play! Just my personal tastes though.
I also agree that that to get the Beatle sound you really have to be the Beatles. But what you can do is continue their constant experimenting with finding new techniques and sounds.
For me a key feature was the use of vocal harmonies. They were really skilled in that area.

"They mostly used four-track tape machines, sometimes with two linked together."

well, not really true. The Beatles were recording for several years before they tried this technique, but they were the first to do so. For the first half of their career though their stuff was recorded in mono. Place the mics at the distances that sound "good", press record, and that's the mix you get. Even their stereo stuff up to that point is pretty much just two track tape, with the channels panned hard left and right, until you get to "Sgt Pepper's" that is. They did try as much as they could, what i just said is a bit of an oversimplification, but they didn't use any real multitracking till about halfway through their career.

well yes, but if someone is using basic equipment today, this means it is very relevant to look at how people have made good use of similarly basic equipment in the past, even if that equipment was state of the art at the time.

I find that stuff interesting for its own sake, though as well. For example the CD reissue of Ten Years After's third album Stonedhenge mentions that to get any stereo panning, they had to rig up a contrivance made of string and bits of wood, attached to the volume controls of two tracks, to create the pan control, because the studio they recorded in only had mono mixing desks. And i am fascinated to listen to Fleetwood Mac's first few LPs because it's clear from the reissues (where some of the stuff from before and after takes has been edited back in) that the stuff is pretty much recorded live, though it has been recorded multitrack. This even includes things like the brass section being in the studio on the day and playing live with the band at the time of recording.

At about the same time, though, Love's third album was being recorded in LA. There are brass parts, there are string parts, plenty of acoustic 6 and 12 string guitars at the same time as drums etc, and all the mixing on the album makes it very clear, from the sound of it, that this album was mainly recorded a track at a time in a very modern style multitrack way.

Paul McCartney, former member of The Beatles, said in an interview on August 6, 2010, regarding 'Outliers':
"I've read the book. I think there is a lot of truth in it [...] I mean there were an awful lot of bands that were out in Hamburg who put in 10,000 hours and didn't make it, so it's not a cast-iron theory. I think, however, when you look at a group who has been successful... I think you always will find that amount of work in the background. But I don't think it's a rule that if you do that amount of work, you're going to be as successful as the Beatles."

Regarding "The Beatles Sound," I learned something watching "Best of the Beatles," the first drummer Pete Best documentary. Klaus Voorman, who befriended The Beatles during their Hamburg club days says that their sound really came from the bass and drums of Best and Stuart Sutcliffe. Sutcliffe was limited but dedicated to a mastery of simple, early rock basslines. Akin to purists like Link Wray or The Cramps, not nearly musically incompetent live, like Sid Vicious. And Best played pounding drums without syncopation. (He was fired when he couldn't play anything but his straight beat for The Beatles recording session for a first UK single.) Voorman said that the early essence was entirely lost when they first came back to play Hamburg without Sutcliffe on bass. So, their recorded sound could be said to be a striving for their early caveman rhythmic power despite having more finesse at their disposal with their eventual fab four lineup.