No - The Eyre Affair is first and they do really need to be read in order. Next is Lost in a Good Book then it's The Well of Lost Plots. Then its Something Rotten and lastly First Among Sequels.
The Big Over Easy and The Fourth Bear are a different series and need to be read in that order.
I started with the Big Over Easy while I waited for the library to deliver the Eyre Affair.
Have to admit I nearly gave up on The Big Over Easy several times as I found part of the plot rather laboured, but really liked Jack Spratt. Thanks to all the recommendations I persisted and am glad I did - the book picked up as it went along. I found The Eyre Affair really readable as a whole and enjoyed it.
For those who have not read Fforde
The Eyre Affair - alternate world to ours, so modern UK, but Wales is a separate country and has been for a long time. UK is still at war with Russia in the Crimea. The heroine of the story is a war veteran and works as a Literatec - special operations - and is basically employed to investigate thefts and frauds of famous books. The whole country is literature mad and there is a lovely scene where she goes out to a production of Richard III with audience participation of the Rocky Horror Show variety. Her father is a renegade time cop, her uncle is a mad inventor and once, when a child, she managed to accidentally step over the boundary of reality and fiction and briefly meet Mr Rochester in Jane Eyre. Then there is the truly insane and powerful villain. Lots of fun.
The Big Over Easy - is a take on detective novels. The whole set up of the incredibly convoluted plot has the mick thoroughly taken out of it on several levels. The world it is set in is detective story mad, all the police detectives are busy looking for publication rights and get promoted based on public fame arising from their serialised cases in various publications. (Rather like Watson on Sherlock Holmes.) The story is based around a new transferee to Reading, which is base of many top name detectives, she doesn't finish up in the glamorous place she wanted, but instead is placed in the Nursery Tale division. This exists to investigate nursery tale murders and is not glamorous. The book follows, amongst other things, the investigation of the murder of Humpty Dumpty. (Hence Big Over Easy boom, boom.)
The parts I found hard work were those centred on the famous detective that the heroine wanted to work with and all his press conferences and machinations.
Definitely onto the sequel of the Eyre Affair when I can get hold of it. Probably will read The Fourth Bear, just not rushing