I seen to remember reading somewhere that there was (or the author of the piece thought there was) a difference of emphasis depending where the word ĉi is positioned, e.g.

Tiu ĉi libro
Ĉi tiu libro
Tiu libro ĉi

Does anyone remember what this was? Or have any ideas of their own?

The last one seems valid only if ĉi is a poetic abbreviation of ĉi tie.

I don't think there's any significant difference between the other two. I use them interchangeably.

Bruso:I seen to remember reading somewhere that there was (or the author of the piece thought there was) a difference of emphasis depending where the word ĉi is positioned, e.g.

Tiu ĉi libro
Ĉi tiu libro
Tiu libro ĉi

Does anyone remember what this was? Or have any ideas of their own?

Looks like it's from Don Harlow's book on Esperanto.

The particle ĉi can be added to give a feeling of proximity to the speaker; the particle for can also be added (though this is less often done) to show distance from the speaker. Traditionally, ĉi is usually placed immediately before the T- word to which it is attached; often, it is placed immediately after. This is not, however, absolutely necessary.
EXAMPLES
tiu libro = that book
ĉi tiu libro = this book (most common usage).
tiu ĉi libro = this book
tiu libro ĉi = this book (unusual usage)
tiu libro for = yonder book
tiam = then
ĉi tiam = now (synonym of )
tiam ĉi = now
tiam for = distant in time (uncommon usage)

I agree with Harlow's comments.

tiu libro ĉi = this book (unusual usage)
tiu libro for = yonder book

ĉi tiam = now (synonym of )
tiam ĉi = now
tiam for = distant in time (uncommon usage)

I've never seen any of these formations in actual use. IMHO there is no difference between ĉi tiu and tiu ĉi (I prefer the former as modifiers usually precede the modified word in E-o).