Manchester United moved three points ahead of Manchester City at the top of the Premier League on Saturday.
A remarkable game at the Madejski Stadium saw all seven goals scored in the first-half, with United carrying their one goal advantage through to the full-time whistle.
It meant Alex Ferguson's side have clear daylight over rivals City who could only take one point from their match against Everton.
In the early kick-off, new Chelsea manager Rafael Benitez is under more pressure to produce a win as his side lost 3-1 to London rivals West Ham.
At the Etihad Stadium, Marouane Fellaini headed Everton in front in the 33rd minute but conceded a penalty 10 minutes later after tangling with Edin Dzeko, allowing Carlos Tevez to equalise from the spot.
The draw maintained City's unbeaten start to their title defence, however it also allowed United to extend their lead.
"In this moment, we are not very strong with our strikers,'' City manager Roberto Mancini said.
"We need them to score more goals.''
City have gone 37 home games without defeat, a sequence stretching back to a loss to Everton two years ago. However, that has not been enough to take command of the Premier League.
United still lead the pack although Ferguson is likely to have had a few words for his defenders at half-time after they conceded three goals inside 30 minutes.
Hal Robson-Kanu put Reading in front, but Anderson equalised and Wayne Rooney gave United the lead from the penalty spot by the 16th minute.
Adam Le Fondre hit back for Reading and Sean Morrison headed the hosts ahead by the 23rd minute.
Rooney began United's second comeback and Robin van Persie made it 4-3 by the 34th when the flood of goals ended.
Next Sunday, United host second-place City, in a crucial top table clash.
Arsenal plummeted to 10th place, five points below the Champions League places, after Spanish forward Michu's late brace gave Swansea City a 2-0 victory over Arsene Wenger's misfiring side.
A cut-price $3.2 million close-season signing from Rayo Vallecano, Michu struck in the 88th and 90th minutes to take his tally for the campaign to 11 league goals and silence the Emirates Stadium.
It was Arsenal's fourth league defeat of the season and their third successive game without a win.
Meanwhile, Arsenal's London rivals Tottenham are busy climbing the table. A 3-0 win over Fulham moved them up to fourth and into the Champions League spots.
"Both (Gareth) Bale and (Michael) Dawson have suffered hamstring muscle injuries"
Spurs boss Andre Villas-Boas
Brazilian holding midfielder Sandro set Spurs on their way with a wickedly swerving 30-yard effort in the 55th minute before a quick-fire Jermain Defoe brace took the game away from Martin Jol's side.
However, Spurs will have to continue their good form without two of their strongest players.
"Both (Gareth) Bale and (Michael) Dawson have suffered hamstring muscle injuries," Tottenham manager Andre Villas-Boas said.
"One looks more serious than the other although both are controllable.
"With muscle injuries it's very difficult but it might keep him out for one to weeks. Dawson a little bit less."
Spurs leapfrogged West Brom who lost to Stoke City after a 75th-minute goal by Dean Whitehead.
Liverpool climbed one place to 11th after Daniel Agger's 43rd-minute header was enough to secure a 1-0 success at home to Southampton and earn Brendan Rodgers' side only their third home win of the campaign.
Harry Redknapp's home debut as Queens Park Rangers manager ended in stalemate after his side were held 1-1 by Aston Villa at Loftus Road.
Brett Holman put Villa ahead in the eighth minute but Jamie Mackie's fine 18th-minute header levelled the scores for QPR, who had Stephane Mbia taken to hospital following a collision with Gabriel Agbonlahor.